Not recently, but I have over the years scaled back or removed collections. It's a very personal choice, so I won't attempt to "answer" you other than to say that I sleep well enough at night, ha.
What I will do is offer 2 pieces of advice as you contemplate for yourself:
1. Consider "sequestering" the pins you are thinking about ditching. For me, I removed them from my pin displays and rearranged what was left. It was a bit of work, especially if I'd changed my mind. But my goal was to see how much I missed them. It turns out, it was a case of "out of sight, out of mind." I didn't think about what was gone, so I determined that I could let them go for real.
2. Ask yourself how hard they would be to replace if you regretted getting rid of them. All decisions in life shouldn't be based on perceived value/cost (it can lead us to cling to things we don't actually want or like, for the wrong reasons). BUT it can help to clarify how strongly you feel about an item. If "I could never afford to replace that" makes you sad, well, that tells you something. If you're more like, "I wouldn't pay THAT for that pin," well, maybe you aren't that fond of it. If it's not especially high value, so this isn't an issue at all, well, your risk threshold is much lower.
There is nothing worse than acting in haste and finding you can't easily undo it. If I regret anything--and it's only the tiniest bit--I wish I'd kept my Designer Queen of Hearts pin. She seems to be very hard to find now, in terms of literal availability, never mind potential cost. But I still don't lose sleep over it. It's just an occasional "I wouldn't be mad if I still had it" than an "I ruined my life."
And honestly, I know everyone is way over Marie Kondo but I stand by the "Does it spark joy?" question for pins. Very often, we decide we "have to" have certain pins or themes, and after a while it becomes a mindless habit rather than a joy. Some people ENJOY being a completist on a theme, and that is great for them. But I dropped being a Dinah completist when I realized I didn't like every pin I was forcing myself to get "because." It wasn't making ME happy to have pins that were just ok or even (to me) kinda ugly.
So don't underestimate the power of asking yourself why you have certain pins or themes and whether they still make you happy!