I think that asterisk is exactly the reason why the range wordings should empower the GM to be in a position of allowing players to be awesome through fiat rather than forcing the GM to justify why a player's range is getting "nerfed" this time. It comes down to design priorities... Should the rules fail safe in a way that allows the GM to use fiat for fun when ensuring everyone has fun is part of GM'ing -OR- Should they be written with some assumption of a high percentage of GM's being adversarial in ways that need restraining so those rules fail secure in ensuring players can trivially challenge even the faintest use of fiat from a gm trying to pursue that fun for everyone goal.
The cover rules do indeed exist, but you are describing leans more into the omitted concealment rules*. With only the cover half of the toolset they provided it's an incomplete toolset on top of having a fairly high bar to meet & that forces the GM to quickly fall back to fiat. Here are the rules for 5e's lowest form of cover
C o v e r
Walls, trees, creatures, and other obstacles can provide
cover during combat, making a target m ore difficult
to harm. A target can benefit from cover only when an
attack or other effect originates on the opposite side
of the cover.
There are three degrees of cover. If a target is behind
multiple sources of cover, only the most protective
degree of cover applies; the degrees aren't added
together. For example, if a target is behind a creature
that gives half cover and a tree trunk that gives three-
quarters cover, the target has three-quarters cover.
A target with half cover has a +2 bonus to AC and
Dexterity saving throws. A target has half cover if an
obstacle blocks at least half of its body. The obstacle
might be a low wall, a large piece of furniture, a narrow
tree trunk, or a creature, whether that creature is an
enemy or a friend.
Walls, trees, creatures, and other obstacles can provide
cover during combat, making a target m ore difficult
to harm. A target can benefit from cover only when an
attack or other effect originates on the opposite side
of the cover.
There are three degrees of cover. If a target is behind
multiple sources of cover, only the most protective
degree of cover applies; the degrees aren't added
together. For example, if a target is behind a creature
that gives half cover and a tree trunk that gives three-
quarters cover, the target has three-quarters cover.
A target with half cover has a +2 bonus to AC and
Dexterity saving throws. A target has half cover if an
obstacle blocks at least half of its body. The obstacle
might be a low wall, a large piece of furniture, a narrow
tree trunk, or a creature, whether that creature is an
enemy or a friend.
All of those bold bits (especially the non-additive one) add up to setting a fairly high bar rarely seen by chance with wide enough presence to make it difficult to simply step a bit into clear line of sight to avoid the cover entirely. 3.x had fairly similar rules for cover but included the other half the toolset for the GM that had existed snice at least 2e. Cover works alongside the more quantum concealment that had a much lower bar
CONCEALMENT
Besides cover, another way to avoid attacks is to make it hard for
opponents to know where you are. Concealment encompasses all
circumstances where nothing physically blocks a blow or shot but
where something interferes with an attacker’s accuracy.
Concealment gives the subject of a successful attack a chance that
the attacker missed because of the concealment.
Typically, concealment is provided by fog, smoke, a shadowy area,
darkness, tall grass, foliage, or magical effects that make it difficult to
pinpoint a target’s location.
To determine whether your target has concealment from your
ranged attack, choose a corner of your square. If any line from this
corner to any corner of the target’s square passes through a square or
border that provides concealment, the target has concealment.
When making a melee attack against an adjacent target, your
target has concealment if his space is entirely within an effect that
grants concealment (such as a cloud of smoke). When making a
melee attack against a target that isn’t adjacent to you (for instance,
with a reach weapon), use the rules for determining concealment
from ranged attacks.
In addition, some magical effects (such as the blur and displace-
ment spells) provide concealment against all attacks, regardless of
whether any intervening concealment exists.
Concealment Miss Chance: Concealment gives the subject of a
successful attack a 20% chance that the attacker missed because of
the concealment. If the attacker hits, the defender must make a miss
chance percentile roll to avoid being struck. (To expedite play, make
both rolls at the same time). Multiple concealment conditions (such
as a defender in a dog and under the effect of a blur spell) do not
stack.
Concealment and Hide Checks: You can use concealment to
make a Hide check. Without concealment, you usually need cover
to make a Hide check.
Total Concealment: If you have line of effect to a target but not
line of sight (for instance, if he is in total darkness or invisible, or if
you’re blinded), he is considered to have total concealment from
you. You can’t attack an opponent that has total concealment,
though you can attack into a square that you think he occupies. A
successful attack into a square occupied by an enemy with total
concealment has a 50% miss chance (instead of the normal 20% miss
chance for an opponent with concealment).
You can’t execute an attack of opportunity against an opponent
with total concealment, even if you know what square or squares the
opponent occupies.
Ignoring Concealment: Concealment isn’t always effective. For
instance, a shadowy area or darkness doesn’t provide any conceal-
ment against an opponent with darkvision. Remember also that
characters with low-light vision can see clearly for a greater distance
with the same light source than other characters. A torch, for
example, lets an elf see clearly for 40 feet in all directions from the
torch, while a human can see clearly for only 20 feet with the same
Besides cover, another way to avoid attacks is to make it hard for
opponents to know where you are. Concealment encompasses all
circumstances where nothing physically blocks a blow or shot but
where something interferes with an attacker’s accuracy.
Concealment gives the subject of a successful attack a chance that
the attacker missed because of the concealment.
Typically, concealment is provided by fog, smoke, a shadowy area,
darkness, tall grass, foliage, or magical effects that make it difficult to
pinpoint a target’s location.
To determine whether your target has concealment from your
ranged attack, choose a corner of your square. If any line from this
corner to any corner of the target’s square passes through a square or
border that provides concealment, the target has concealment.
When making a melee attack against an adjacent target, your
target has concealment if his space is entirely within an effect that
grants concealment (such as a cloud of smoke). When making a
melee attack against a target that isn’t adjacent to you (for instance,
with a reach weapon), use the rules for determining concealment
from ranged attacks.
In addition, some magical effects (such as the blur and displace-
ment spells) provide concealment against all attacks, regardless of
whether any intervening concealment exists.
Concealment Miss Chance: Concealment gives the subject of a
successful attack a 20% chance that the attacker missed because of
the concealment. If the attacker hits, the defender must make a miss
chance percentile roll to avoid being struck. (To expedite play, make
both rolls at the same time). Multiple concealment conditions (such
as a defender in a dog and under the effect of a blur spell) do not
stack.
Concealment and Hide Checks: You can use concealment to
make a Hide check. Without concealment, you usually need cover
to make a Hide check.
Total Concealment: If you have line of effect to a target but not
line of sight (for instance, if he is in total darkness or invisible, or if
you’re blinded), he is considered to have total concealment from
you. You can’t attack an opponent that has total concealment,
though you can attack into a square that you think he occupies. A
successful attack into a square occupied by an enemy with total
concealment has a 50% miss chance (instead of the normal 20% miss
chance for an opponent with concealment).
You can’t execute an attack of opportunity against an opponent
with total concealment, even if you know what square or squares the
opponent occupies.
Ignoring Concealment: Concealment isn’t always effective. For
instance, a shadowy area or darkness doesn’t provide any conceal-
ment against an opponent with darkvision. Remember also that
characters with low-light vision can see clearly for a greater distance
with the same light source than other characters. A torch, for
example, lets an elf see clearly for 40 feet in all directions from the
torch, while a human can see clearly for only 20 feet with the same
There are two types of protection a character can have. The
first is concealment, also called soft cover. A character hiding
behind a clump of bushes is concealed. He can be seen, but
only with difficulty, and it’s no easy task to determine exactly
where he is. The bushes cannot stop an arrow, but they do
make it less likely that the character is hit. Other types of con-
cealment include curtains, tapestries, smoke, fog, and brambles.
The other type of protection is cover, sometimes called,
more precisely, hard cover. It is, as its name implies, something
a character can hide behind that will block a missile. Hard cover
includes stone walls, the corner of a building, tables, doors,
earth embankments, tree trunks, and magical walls of force.
first is concealment, also called soft cover. A character hiding
behind a clump of bushes is concealed. He can be seen, but
only with difficulty, and it’s no easy task to determine exactly
where he is. The bushes cannot stop an arrow, but they do
make it less likely that the character is hit. Other types of con-
cealment include curtains, tapestries, smoke, fog, and brambles.
The other type of protection is cover, sometimes called,
more precisely, hard cover. It is, as its name implies, something
a character can hide behind that will block a missile. Hard cover
includes stone walls, the corner of a building, tables, doors,
earth embankments, tree trunks, and magical walls of force.
* The word concealment does not appear to be in phb dmg xge or tcoe. It does appear in VRGtR(pg70), but it's a very different use & talking about how tatyna is hiding from strahd.
@Hriston Yea, they used to be in an actual book in the past too (2e dmg139/140 & I hear 3.0 dmg)
