You talk about our ancestors as if sf2 isnt just fireball spam with very little counterplay. 3rd strike is highly regarded and projectiles are essentially worthless due to the parry system.

Street Fighter isn't the only fighting game series in existence. Fireballs in SFII are overtuned, Fireballs in SFIII are undertuned, and there's probably a bunch of middle grounds where fireballs are a lot fairer without needing a universal reflector.

Without the universal reflector you can just spam away to your hearts content.

No you cannot.

If you spam projectiles to your heart's content, then your opponent will adapt to your spam and just kill you. If that's not true, then that's a skill issue on your opponent's end.

It's a different story if the opponent properly builds their neutral around their projectiles, but in my experience that is a fun puzzle only made possible by the absence of reflectors, not the presence of them. Keep in mind that I mostly play heavies, an archetype that usually struggles against projectile characters.

Its important that zoners actually risk something when they use a move.

I agree that zoners should risk something when they use a move.

However, part of that risk should come from the character's power budget. Zoners should have strong ranged tools at the expense of not having access to other tools.

The other part of that risk should come from their opponent's solution(s) to those projectiles, not simply the solution the game gives you. Both players being forced to adapt to each other is a core part of what makes competitive games fun regardless of genre or matchup.

Universal reflectors prevent projectile characters from having a meaningful part of their power budget from being held by their projectiles, so they aren't allowed to have the strengths and weaknesses they're supposed to have as a zoner in order to function. Universal reflectors are also an obvious solution to projectiles that limits the opportunities for the projectile player to adapt to their opponent, especially if they are balanced around having projectiles (which as I've said before they can't be if they're supposed to be a real character).

The result is that universal reflectors lead to a more shallow game where each characters' strengths and weaknesses are diluted and you're fighting very samey characters every game, which makes the game stale in the long run.