If you don't want to read my mini-rant, go ahead and skip this paragraph and read the next one where the fix is; I certainly won't be offended, I just have to get something off my chest. Is there any particular reason, Ubisoft, Valhalla is literally the only modern game in my library that straight up insists on AA? You can't even disable it in a config file. Also, TAA is absolute trash. It's notorious for turning sharp sexiness into a blurry disaster. It's like looking at a masterpiece through a smudged lens. Weird choice. On top of that, your options are to lower it so the blurriness just gets infinitely worse. High/Medium/Low only AA options in a 2020 video game. Tight.
Anyways, here's the "fix." There may be a way to do this on an AMD card, but I'm not familiar with the software; sorry guys. If you've got the Geforce Experience running and the game is launched, hit Alt-F3 to open the Game Filter overlay. There, choose a slot (1, 2, or 3) and hit Add Filter from there. You'll notice Sharpen is an option. Click it and set the slider as needed. Fantastic, a much-less blurry game at a minimal FPS loss. Oh except, and I'm sorry but I have to throw just a little more shade at Ubi, because the AA cannot be disabled, you're effectively just putting lipstick on a pig while losing substantial FPS from the AA (the pig). My system is decent -- Ryzen 9 3900x, 64GB RAM, RTX 2060 (decent) -- but I'm at a native 1440p and with AA on high, which is basically mandatory, getting 60 fps even with a bunch of crap turned down to medium or high at best is nearly impossible. There's no excuse for this. Let us disable AA like every other game.
Hope that helps. This is kind of a going away tip from me, since I've already uninstalled the game. Maybe they'll patch it in the future, idk. I don't really care. Good luck.