Vayne is a problematic design by nature who also isn't a problem most of the time. (keyword: most)
her kit is basically designed to do one thing: Single target damage. everything in her kit is single target and amplifies her auto attack damage in someway. this leaves her very feast in her famine and entirely reliant on if she can get to her items in the first place. with her current kit, her laning will always be trash tier. even now it is pretty bad.
What this also means though is if there is ever a world where the meta involves ADCs slow scaling and lane bullies simply aren't doing their job hard enough to justify being picked, it means she is instantly top tier. Yes, vayne can go from literal trash, to god tier with one patch if the right things fall in place.
This patch you had nerfs to lethality, no compensation buffs on the lane bullies (jhin is probably only one who didnt need it), fervor being heavily nerfed so warlord's is the go to. This mean vayne gets to scale. she can survive lane and just farm up to her items. if she gets a gank or two watch out as well because a fed vayne is something no one wants. But right now, even without ganks she has NO problem surviving lane. It was the perfect storm of events
1.) vayne gets Q crit buff (she needed this as before you had no reason to pick vayne as the reward was not worth the risk by being shit on early)
2.) armor pen gets heavily nerfed, lane bullies weakened.
3.) Fervor gets heavily nerfed, lane bullies weakened even further
vayne now gets to just scale up into the monster she is. I personally have been somebody who never minded vayne because she is easy to poop on in lane usually. right now, she isnt. so they either have to buff lane bullies, or nerf vayne. personally, the Q crit changes are no longer necessary now that lane bullies have been hit so damn hard. revert those and she should fall back in line. they also gave her the ability to use Q on towers. I think that should stay, but only the Q crit change needs to be revereted.