Its a problem but it isn’t a major problem. I am using rspamd without any sort of exotic configuration (basically just enabling things that are provided, not my own rules) and I only get a few spam messages leaking through a week. Maybe slightly worse than GMail but not considerably slow.

IMHO the only real missing thing out of the box is contacts checking. Which is a huge thing because it is great to have reliable delivery from contacts. But my false-positive ratio is so low anyways that it isn’t a big issue and things like the known_senders module mostly mitigates it.