Well I think you're completely right, in a way. But I also don't see the problem with people telling other people to not use the software or to complain about it. They are totally in their right to complain about stuff. Now obviously if the complaining involves requiring people to work for some feature you want, that's entitled and wack. Same goes for throwing a fit because maintainers went for systemd instead of your own favorite init system.

But being open source doesn't mean people shouldn't or can't just say "this is bad" or "don't use x" or even "this X feature doesn't work when using Y" (now If what they are saying isn't true, sure we should call them out)

It's normal and in fact I think it should be encouraged, as not everyone can be aware of potential problems they could have with a piece of OSS that is already known in some obscure dev mailing list. The more people are informed and aware of potential issues, the less they will be surprised and complain about it when they start using it.

(Fwiw I love btrfs, and I think it's very reliable)