I travelled with Flixbus multiple times when the sector was still booming about two years ago. I don't understand the complains. Flixbus has comfortable seats, you can charge your phone and they have very fair prices for snacks and drinks. Of course, you do not have infinite space if you have long legs (but more than in a common bus) and the Wifi could be laggy sometimes. But hey, they had free wifi before the Deutsche Bahn was even thinking about it! And a online media center with quite a variety of films free to watch. They really made an effort to provide good service and offer a comfortable ride, so my experience.

I switched to ride sharing (not like Uber - but a in a way where someone who is taking a certain route anyway fills up their empty seats) since Flixbus got more expensive when their competition died out.