Because "defending yourself" is a physical action, not a mental one.
so every fight is decided purely by who is physically stronger then, nobody uses their brain as they fight? a physically feeble master will always be beaten by a brute with no combat experience.
Planning attacks is something the player personally does,
not in the same way, the rogue player doesn’t have to describe where and what angle their dagger goes in at when they sneak attack, the bard player doesn’t have to figure out what inspiring thing they say whenever they use bardic inspiration, hell, i'm basically just asking for more stuff like maneuvres.
that's...literally the point of having choices in combat and learning how to make better choices over time. "Targeting weak points" is not meaningfully supported by the game's rules, and every system I've seen attempt to do so is far too fiddly to actually be worth engaging with.
Know Your Enemy exists, that's not fiddly, just pull that down out of battlemaster and put an improved version of that in the baseclass.
I'm not saying it's not possible to have Int-based mechanics for purely martial characters, even Fighters. I'm saying all the ones I've ever seen that would actually be enjoyable to use and play around with only really make sense as a subclass-specific thing, not as something absolutely every Fighter can access.
you keep saying this but you;re not elaborating on what these abilities are that 'could only ever exist as part of a subclass', let fighters be smart.
And, as has been noted multiple times in this thread, whatever the mechanic is, you have to lock it behind at least 2 (and preferably 3-4) Fighter levels, otherwise people will just dip for it. Heck, there's a whole category of builds that start with Fighter 1 before going fully focused on a caster thereafter, with Bladesinger Wizard being a prime pick. And if you're already going to put it behind Fighter 3...is it really that much of an issue for it to be a subclass-specific thing? Perhaps different options for Battlemasters and a hypothetical Int-focused subclass, to represent how there are different ways for Int to be useful in combat?
I completely agree. I just don't see that allowance manifesting as something absolutely every Fighter gets and does.
i propose removing multiclassing as the solution to this issue, it only ever caused problems, but more seriously, i do think this is something
every fighter should get, people complain that the fighter is generic, well this gives it more of an identity, the General, the Tactician, the unbeaten Warrior, they don't have to get it all at 1-3, spread some of this out more across levels, make things dependent on having fighter levels specifically.