So if I want to play a gladiator or a duelist, is that a knight, a skirmisher, or a warlord?
Fundamentally, I don't feel fighter is such an overwhelmingly strong class that you need to silo out capabilities that all fighters might have to some extent to keep them from dominating over the other classes. Like when is the last time you heard someone say, "I'd like to play a spellcaster, but the fighter is just so much more versatile and powerful both in and out of combat that it just doesn't make sense to play a spellcaster."
It's weird because almost no concept gets cut down into smaller pieces than "fighting man" by people attempting to extend D&D and yet the reason mechanically you cut an archetype into smaller pieces is because the archetype would have too much stuff otherwise. So you could justify splitting cleric and wizard to avoid a single class with access to all the best spells, but I think you have a hard time justifying splitting "Good with a sword and shield" from "Good with a bow" or "Good at fighting and moving at the same time." You don't need a class for every weapon and every aspect of martial prowess, so that we have the "Porter" class that is good a carrying things and hiking and a "Slasher" class that is good with whips and so forth.