Riot wants Yasuo to have reduced passive shield and have his windwall up more frequently.
Yasuo - Exploring weaker shield and more frequent windwalls early game. Goal there is to test shifting defensive power so he's similar or slightly stronger against ranged match ups and weaker against melee, making it clearer how to deal with him if he gets picked/give him situations where he's a better choice without just being a better generalist. We're still looking to do larger work on him at some point too, this is initial investigation, not a comprehensive set of long term changes.
I think the windwall should be changed to only block Ranged auto attacks and not every single projectile, which would actually make him stronger against ranged champions and not a generalist.