Gluster was that for me

Yup, still get nightmares about glusterfs.... still have one customer running on it.

I heard it got better, but we ran into the BOTF (billions of tiny files) issue around 2016. (For a genealogy startup this was a serious issue)

Ah, another one! Yep, also same, before ceph days at least (although I've had my own, albeit self-inflicted, nightmare there too).