well I got a few answers for you, bud. IDK if you know how to play against him, but since everyone bans him and doesn't learn how to fight him I'll say it anyway.
for starters its really strong on how much damage it mitigates, but it also refreshes super fast
Well "super fast" is subjective, and by saying "how much damage it mitigates" is telling me you are trying to burst straight through it. if you are a mage or a marksmen, it's no problem at all. All you have to do is hit the shield once with anything, which is further enforced by the shield being able to be taken down by 1 damage. There is SO many people saying "it blocks too much damage" when it can be taken down by 1 damage just as easily as it will be taken down by 1k damage.
For a mobile champion like Yasuo
Well he isn't really mobile outside of the lane, after all he can only dash to an enemy. Meaning he can't really catch you without allied champions or minions. Basically he's situationally mobile.