25k rep early adopter. I stopped using it when the librarians got out of control and it no longer was about helping people but instead about being a perfect library of provable knowledge where most users started to be categorised as problematic to that goal. Particularly users who were less competent at expressing themselves in English.

Other things that irked: librarians removed all the flavour from many of my answers over time (not only swearing but also quirky phrasing or choice of metaphor), librarians would close discussion topics that were useful (e.g. what's a good tech choice for this usecase today?"), or librarians would close new questions I was in the middle of penning a non-trivial answer to because they'd misunderstood what the user was actually asking (e.g. poor English).

Since the days of newsgroups I was seeking a place to pay off the knowledge debt I'd obtained through the glorious advice that luminaries such as Jon Skeet and Nicholas Paldino had given me in the past. SO stopped being that place after all the basic questions had already been asked. There was a kindness and endless patience that the newsgroups programming crowd had, that I feel like we lost with the SO librarians.

I appreciate that I had a different perspective on what I wanted SO to be than the founders but I really perceived the frustration new users had with the approach to moderation and it made me upset to the point of not wanting to use it anymore.