[ymolodtsov]

Nobody says it's proven. It's just the best what we have so far. Any theory that would work just as good and explain anything on top would be welcome.

And I can say myself that not everyone agrees with that discovery: http://www.astronomy.com/news/2019/09/astronomers-cant-agree...

Well, people still debate about the Bullet cluster. But if it's correct then it's actually a good (relatively) confirmation for some sort of dark matter. It two similar galaxies look the same but have dramatically different mass distribution then there's some mass we don't see yet.