Ah. Now I get what you've been saying, and I get where the disconnect between us is. This:
Is backing away more dangerous than standing still?
Simply put: Yes, backing away is more dangerous than what you call "standing still"; because what you call "standing still" is not standing still.
When engaged in melee, whether one is rolling the dice for an attack or not, one is assumed to be
constantly engaged in combat (not explicitly stated in this edition, but an assumed conceit throughout D&D's history). One is constantly attacking, parrying, feinting, dodging, ducking, repositioning (within your 5-foot square if using a battlemat/grid rather than theater-of-the-mind), etc., etc. One is most certainly not "standing still."
In effect, one is under an
Engaged Condition, though there is no real altering of your character's capabilities other than they must
Disengage to end the condition.
In my own houserules, I actually list
Engaged as a condition, to avoid confusion with my players.
Also, a melee attack roll is not representative of a singular attack*, but a roll to determine the likelihood that a rounds worth of your attacks may have succeeded in inflicting injury on your opponent. Multiple attacks means multiple dice rolls. Multiple dice rolls mean a higher percentage chance of success during a round.
It's the disconnect between the fluid and complex aspects of a real combat, and the artificial breakdown into a turn-based mechanic.
With the assumption that one is constantly and actively engaged in combat with an opponent, and the assumption that your opponent is also, the conclusion is that one cannot simply stop fighting and step away because your opponent hasn't also stopped. They are still
actively trying to kill you, therefore you must continue to defend against that or suffer injury.
Defending against those attacks while also disengaging from an opponent requires actively maintaining focus on that opponent, using misdirects or similar actions, and moving away in a controlled manner. Thus a
Disengage Action.
If it was fencing, disengage would be a combination of
Displacement or
Feint (or
In Quartata,
Passata-sotto, etc.) with the purpose of covering a
Retreat, or using a natural break like a
Recovery to initiate a
Retreat. (It wouldn't be called Disengage in fencing since
Disengage is actually a type of attack).
What you can't do is simply drop your guard and walk away, which is what you're doing if you don't take a Disengage action.
If it makes more sense for you, perhaps rename
Disengage as
Retreat, which is basically what it is. I'm thinking the writers of the game didn't call it
Retreat though, in order to keep it from being confused with things like the
Expeditious Retreat spell, or the idea of a group
Retreating from an Enemy(though in many ways it's the same thing, just on a larger scale).
Maybe call it
Individual Retreat, though I'm not sure if that's any better or not. (I know I don't like it...too clunky.)
Anyways...Does this make more sense? If not, that's cool. It just means we likely have different narratives in our heads as to what's going on in D&D combat, though in the end, the mechanical effects are the same.
Cheers.
*Ranged attacks are singular attacks, melee attacks have traditionally not been so. However, I did notice that the PHB says
"With this action, you make one melee or ranged attack." This is a bit of a departure from the concept, though I believe it was meant less to reimagine the concept as it is meant to inform the player to take one attack
roll, and not confuse them with the idea that an attack roll actually represents
all of a character's attacks in a round. But if one wants, you can still think of it as one attack, even though you're actually making multiple attacks during a round, and just consider it as the one attack that
matters. The one attack that is actually a fully focused, intensive attempt to injure your opponent, rather than just an attack to set up a real attack. Multiple melee attacks can then simply mean that more than one of those multiple attacks you make in a round are real, fully focused attacks.