Mumble rappers aren't the reason why some rappers can't make decent money nowadays and will never be the problem. Every year we get amazing projects out. Mumble rap was just a fad tho, but together with drill, it brought some needed high energy to this music, that is seen in other stuff too (like Jpegmafia)
Just do you and good things will come (if you have a certain level of quality and interesting music to offer). While it is sad that rappers that have been killing it for years like Tragedy Khadafi don't get paid enough, but sometimes these rappers can only fault themselves. There are people like Aesop Rock, Slug and Tech Nine that have been on the scene since the 90s and keep supplying great shit to this day. Same with Roc Marciano, altho his solo career did start later.
Rap music is in great space. While I'd rather see some other acts be in place of Eminem, Kanye and Snoop Dogg, rap is doing good.