To the bolded part...
Up until a foe cast anti-magic field, or you encounter a beholder, or you are faced with other casters that shuts you down with counter spells.
and then you ONLY have the same weapons/armor and number of attacks of a fighter... wow almost like that 'downgrade debuff sucked' was where fighters started
(Okay not 100% the fighter up to level 10 has 1 action surge 1 second wind, and 1 feat on you)
Then the fighter looks at you and say: " Welcome to Helldritch's type of games."
you mean when you go out of your way to turn the caster into a fighter... for 1 encounter.
This is the problem with an all caster party. Too much reliance on magic will lead to these type of encounters very fast.
and never have I seen a all caster party that doesn't have some way to handle this (wait... once, we did have an all sage group once and as such our diviner, transmuter, knowledge cleric, tomb feylock (that had 0 attack cantrips) and rogue (arcane trick)/iullusionist who didn't carry a weapon.... they were shut down by ANY combat though since between them there best offenses was magic missile, and weapon of faith) but that game had little to no combat so it was okay)
lets take your things one at a time
a foe cast anti-magic field
maybe counterspell... if not fall back to weapons. most likely this shut down any magic the caster had, and if they can cast that high a spell most likely they NEED magic as much or more then us.
i mean it's not our most common enemy (normally anyway) but I would say we have dealt with this more then a handful of times. I can say I can't remember a single death from beholder since 2e... wait maybe 3e (but that one also was epic and had class levels and a name so not sure it counts).
I had an encounter with 3 beholders onraised terrain and the over lap of there central eyes shut off magic to 90% of the room, and in the room under them were slave/monsters so the PCs had to fight with no magic against a bunch of brutes... but beholders have a REAL BIG flaw(especialy in 4e and 5e)... there main deadly attacks are magic rays, and so they can't use them on creatures in the antimagic cone.
faced with other casters that shuts you down with counter spells.
this one is common/uncommon.
we kinda of MAD counterspell. as a DM I pull it rarely and in exchange my players pull it never. HOWEVER if a PC does use it my next caster will have it... if the PC keeps useing it so will NPCs and we have found as fun as a "gotcha" every now and then is fun, counterspell into counterspell into counter spell is NOT fun...for any of us.
However back in 3e we did this alot.
in an all caster group that counterspell is common, I find the PCs can out counter spell the NPCs more then the other way around
Or even worse, you fight in a wild magic zone...
Okay... so you get a gotcha once (maybe) remember our casters have melee and ranged weapons.
The Hexblade and the wizards were almost crying "UNFAIR!". While the fighter and ranger were not deter one iota about the situation.
Did the Hexblade forget he with NO MAGIC is still an equal fighter? and why would the wizard complain... this is just an excuse to save spell slots to mangle the next encounter?