The impact of magic items absolutely varies as you note, that was my point. a fighter who's bread & butter is swinging a sword multiple times a round & being hi(or whiffed on) by baddies will benefit significantly more from magic weapons & armor than a caster who almost never casts more than one spell per round & might not even have armor proficiency will benefit from magic weapons & armor
My point is D&D places this power in magic item whereas the 13th level anime swordsman, manga thief, or movie gunslinger has them all inherently. They are already moving 100 feet, making 5 attacks a round, have 18+ AC, has high damage range attack, and has advantage to initiative.
D&D puts martial power in magic items where in other media where casters and masters stand equal the martial have said power within themselves.
The fighter doesn't need +2 sword, +2 plate, wings of gliding, boots of speed, gloves of strength, belt of strength and goggle of night vision in non D&D media. They get those abilities at level up.
Yes some media has very durable mages, Naruto is a good well known example where mages & martials stand side by side but is far from the most extreme(it's just well known). The only totally nonmagic individuals in the entire series are the but of a disparaging joke made at an obnoxious stereotype d&d happens to still embrace with one class. d&d does not design for the sort of baseline assumptions required for those sorts of media though & bizarrely there seems to be a group saying they want arthur without Excalibur or its sheath to compare to morgana mordred merlin and the magic item clad magic using characters from those sorts of media. Point out that Arthur has Excalibur & Excalibur's Sheath when comparing his capabilities to those other types though & people cry foul as we saw earlier after an example was given. @Minigiant might desperately want a martial pc that does not need magic items to keep up with magic item sporting characters, but that is some other system because d&d along with its genre is swimming with magic items and said pc will just be slvonkers broken and silly overpowered when it adds those magic itemsjust as *but my character concept really requires the game let me gestt multiple classes each level so the problem is d&d not supporting those characters" would be
Ain't no pure casters in Naturo. Everyone is a fighter/rogue or fighter/rogue/caster.
Why?
Because in most combat based fantasy anime/mange/manhua, when a martial type engages a caster type, the caster needs to be higher tier or they are on the backfoot. And if the caster is in the martial type's preffered attack range... the caster is dead. Not slightly beaten up or or lost 25% HP. They are dead without plot armor. And the martials can do this without magic items.
Magic items just enhance the martials there to make the combat interesting.
The top martials in Naruto, Bleach, One Piece,Kenshin, Slayers,Berserk, and preZ would mess up somemonsters and caster of D&D with mundane gear in fantastic fashion in ways a level 20 fighter would dream about.
Hawkeye, Black Widow, and the powerup JL versions of Batman and Green Arrow would do the same.
The point is D&D nerfs its martials by stripping some of their power and placing it into magic items in order to make an exciting collect-a-thon.
However this shouldn't be necessary. Martials could have magic items be true bonuses like how casters treat them. They could have some of their power given back to the base classes. The only issue is the martial classes would have a lot more class features.