At the moment Flixbus is usable and they have not been enshitified with CAPTCHAs. You can even buy tickets with cash without being penalized (same prices for everyone in Europe… Americans are charged €1 more for some reason).
In most of the country the train is faster.
I guess you often don’t need to transfer for domestic trips. Trains move faster but as soon as you need to transfer the slow train takes about the same time as a Flixbus on trips ~3 hours or less. E.g. Flixbus to Amsterdam is 2 hrs 45 min for €20 return. The slow train is double that price at best and only 15 min faster last time I checked.
Anyway, Flixbus is the only decent mass transit option. So I’m barely in the game. As soon as Flixbus does something lousy like putting their website on Cloudflare or blocking Tor, I’ll probably start looking for car options. That might just be a matter of time. The web gets worse every day.