Those are the very same people that if a mythic martial existed as an option would have no problems playing it
The issue isn't whether or not it exists, but whether it and its counterparts represent something the game should have more of.
If you're in the camp that sees Casters as fundamentally flawed game design, having Martials chase them up the bad game design tree isn't how you address that.
Unless we just
don't care about whether or not its bad design, at which point I can only throw my hands up and say have at the resulting mess.
Generally speaking if you took martials and jacked them up to the Casters level, or worse made them even more broken as some have said they want, then the game just breaks down further because it fundamentally can't support the weight of what even a moderately sized party could bring to bear.
With Martials as they are now, the game already strains when you approach 5+ players. Martials chasing Casters is going to put that strain at 3+ easily.
You would have to completely upend the games entire design philosophy to avoid this issue, and not to mention you'd also need a dearth of content to support people so they know how to actually run the game, because old adventures ain't gonna cut it.
Like, keep in mind, most everyone says the game breaks down at level 10+, and pretty much any DM will tell you playing pass that level is very difficult to run. Throwing jacked up Martials into that mix is not going to result in improved experiences.
You may not have to be jealous of your Caster buddies anymore, but now you have a nonfunctional game thats incapable of supporting the weight of extremely poorly designed classes.
And mind this is something I had to deal with with 5e in making high level play worthwhile to stick around for. Even Martials at T4 as they are now take effort to run a game for, and nevermind the casters. Theres a reason why in 5e I can run a Dragon, 9 Arch Mages, and thousands of Orcs (6 Dragons if we want to skip the homebrew involved in that, as thats the vanilla equivalent) all as one big encounter, and its generally because you have to.
And to bring up my game again, thats all part of philosophy Im designing it with, because despite the effort to make it work, high level 5e was still a lot of fun and the sheer chaos that results is something I wanted to capture in a package that makes far more mechanical sense.
Thats how my game ended up incorporating a gradual shift from dungeon crawler to high octane wargame. The kinds of crazy chaotic nonsense my Classes can get up to by level 30 literally can't function outside of a wargame without some serious Monster design work that would only ever make sense for bosses, not your random mobs. Hence, the use of bespoke Horde rules to make the game work and bridge the gaps so its seamless, mechanically and in the fiction, to go from taking on an entire armies as a 6-person party to fight 6v1 with a big bad.
Its the same bandaid I use to put 1000s of orcs on the field in 5e without turning it into a nightmare, but now its built in and integrated with everything as a unified design direction.