I dont get why nobody complain about vayne

Because, in order to make rageblade work, she needs to autoattack 8 times. That means, she has already dealt 6000+ DMG through AAs only, not counting silver bolts. So, if she gets to the point were she can make rageblade work, she probably already won a fight...

That is, unless we're talking abojt bruiser vayne, which doesn't make whole a lot of sense

I cri when Vayne takes Rageblade.

6... Not 8.

And you can build Rageblade stacks on anything you can auto attack.

Well, neither the most popular build nor the highest win rate build on Vayne currently uses Rageblade. So either players just haven't caught on to using it or it isn't as good as you think. In the larger scope of things, Vayne has a sub- 50% winrate overall being 14th out of the 16 ADCs available but is picked 4th out of all ADCs. So it stands to reason that players just don't perceive Vayne as a threat relative to other ADCs.

Maybe Rageblade is good on Vayne, maybe not. But why complain about a champion that despite popularity isn't winning the majority of it's games?