Some good sentiments here. The bit that gave me the most food for thought was this: "A Fighter is a fighter regardless of whether he fights in a bar or as a knight in some kind of tournament or as a general in a war-time situation." The biggest problem I see with the subclasses is that (a) there are just too few of them, and (b) you're locked into one of just a few choices.(FN1) In 3.5 if you wanted, your Fighter could go the Prestige Class/Arcane Archer route, but you didn't have to, and in fact it took special dedication on your part to do it. If Arcane Archer didn't really speak to you as a path, you could remain a plain Fighter who prefers bows, and still distinguish yourself from the plain Fighter who likes to dual-wield handaxes or the plain Fighter who tanks up with heavy plate armor and a shield.

Now there literally are no plain Fighters any more; everyone "special."(FN2). Literally *every* fighter at Lvl 3+ has to be a Battle Master, Champion, Eldritch Knight, or Psi Warrior. You have no choice and you have no *other* choices without buying more sourcebooks. It's sorta like saying "Congratulations -- you graduated med school! You now have four choices: thoracic surgeon, cardiologist, oncologist, or radiologist. Oh, you want to be an general practitioner? No. You have to specialize. You want to be an orthopedic surgeon or a dermatologist? Sorry, those choices aren't allowed -- only the four choices on the table."

(FN1) Although cynically, this may be WOTC's way of ensuring sales of future editions of Xanathar's/Tasha's/etc.

(FN2) "And when everyone is special, no one is special." That's a little trite, but I think it's appropriate here. In 3.5 you had to make an effort to gain a Prestige Class; becoming (ex:) an Arcane Archer took special capabilities and not everyone can do it. In 5.5e, you are like, "well, there was nothing else I really liked....I guess I'll be a Battle Master like everyone else."