I played Dota 2 from its first beta release, and many years after. Eventually stopped about 2 years ago. In that time I put 4 digit sum into that game, and received nothing that would give me any gameplay advantage. I did it to support the game, that also worked on Linux.
I understand that MTX are not ideal, but there are very different approaches to them. And at least in Dota 2, I can and did support it.