It's almost like people are complaining more about Vayne after her minor nerf

On the basis that Riot is showing favouritism towards flashier champions. While this isn't untrue, it's still kind of unnecessary to complain about it, and here's why.

It's a step in the right direction. Vayne has a larger playerbase than most other champions, even if half of that playerbase are just people playing her because she's strong. It makes sense to take things slowly. Remember the outrage players expressed whenever one of their champions was nerfed/reworked poorly? I don't know about you, but I don't want to go through the experience of thousands of angry Vayne mains storming this place, demanding that the nerfs are reverted.

It's logical to take things slower. The reason a lot of reworks have gone poorly is because the champion was changed too much, and not in a way that their playerbase wanted. Recently, we had Morde, whose solo lane potential was gutted, and made into one of the strongest bot lane carries in the entire game. Even though he was strong, a lot of Morde players were against the changes. Back to Vayne; Riot probably just wants to take her nerf bit by bit, so they don't accidentally gut her completely. A small change, even if it's barely noticeable, is still better than nothing at all. At least they're looking at her.

Of course, it would be preferable to treat every champion nerf/rework/buff as carefully as this, but again, given the nature of her playerbase (not trying to generalize, but the stereotypes are true to some extent), I can see why they would hesitate to make bigger changes.