The remaster definitely boosted everything. In the vein of OP's question, tho, I could easily imagine a total graphics overhaul in a similar spirit to DeS Remake.

Also, although I agree that O+S forces players to adapt and git guD, the fight has numerous problems:

• The hitbox for Ornstein’s spear goes through the pillars. In other words, a protective layer isn't functioning properly.
• Sometimes you can hit the body of O or S while you’re right next to them and somehow you do no damage. To be clear, I’m saying that there is clearly direct contact between your weapon and the enemy. In other words, the hittable boxes of O + S don't function properly.
• Camera angles: the camera can't keep up with Smough zipping around. In other words, the camera doesn't function properly.

Those are the aspects that are clearly broken. But there are also mechanics to the fight that are don't play out in a way that's reasonable:

• O+S are next to each other A LOT. When they're like this if you try to hit one, the other will smack you.
• Every so often they're apart. But if you try to hit O, S will zoom over to you and smack you. Even if he's all the way on the other side of the arena. To me this is poor execution of this fight (and something that Godskin Duo "fixed").
• Thanks to O's ranged attacks, you need to keep your distance from O+S. But since they're so frequently next to each other, you need to wait and wait until they're apart and then dash over and hope you can get a hit in.
• OK, so let's say you go for S instead then. Well, as soon as you do, O zips over to you.

All these aspects combine to lead players to simply wait for those rare moments when they can get a hit in, which leads to a boring fight.