They're the "easy way out" that creates problems instead of solving them. That's why they get grouped together.

Also, sorry I realize I answered "why is muun included" and not "What problems does muun have"

My first gripe with muun is that it calls itself a lightning wallet. Muun is not compatible with the features you expect out of lightning network wallets such as lnurl-auth so when someone complains about the lightning network and you find out its because they're using muun, that's very annoying.

The submarine swaps only work in a low fee environment. In a high fee environment, you had people complaining about the lightning network. When the complaints were about tx fees to open a channel we could recommend tx batching to save on fees, when the problem was that they're a muun user, our only advice was "stop"

Muun's recovery mechanism is not part of any known spec and of course that makes me suspicious about the claim that is even self-custodial. However, as I don't have evidence that muun is custodial, my grievance will instead lay on the fact that its backups are out of spec.