Rarely, I see Java or Go instead for the backend. I cannot recall the last time I saw more than three languages in production for anything nontrivial. I've seen companies significantly larger subsisting on one language for backend (even in microservice architecture!) and one language for frontend. That's not to say there is no sophistication, just that the number of actual technologies in play is slimmer.
This isn't a comment on GitLab's utility or stability, of course. I haven't worked with them in this context, and I'm not a user. I'm just pointing out that, assuming those dependencies are all for GitLab and not e.g. git itself, that is quite a stack to maintain. I don't know if we can extrapolate that to a systemic issue with GitLab that caused a data loss incident, though. That seems uncharitable.
