Wow, this is a really loaded topic for me.
I think one thing I would change is being so open online. I was really naive about it all, and it cost me dearly.
I'm not sure there is much I would change about my SL journey. The negative stuff happened outside of it. My time in SL was pretty magical, especially the early years where we were building something amazing that had never existed before. As SL grew, I lost that feeling, but it was still something totally unique to have been a part of. I don't regret that for a second. Good, bad, ugly, it's all part of the process and I cherish that time.
I haven't really "left" SL per se (and my sim bill reflects that because I keep procrastinating on tiering down to just my 4096 lifetime or something a little over that), but my time has been severely limited the past few years. When I do go in, I have fun and enjoy myself, but lately it seems the only time I have gone in has been for memorial services. I wish I still felt that spark of excitement and connection with SL. It's not completely dead, but very faint.
Ultimately, for me, it has always been the community of friends I've made that makes it all worthwhile. I started out in The Sims Online, then moved to There, then to SL, dragging various people along with me each time. I just recently reconnected with the very first person I ever met in The Sims Online, and it was like no time had passed at all. She recently came back to SL after a long absence, and the first thing I said is "Why does your avatar look like Melania Trump?".
I've also developed a strong attachment to the people in our Discord server. We talk, play games together and laugh, which I love. It's not the place, it's the people, and that has been a constant for me even as the environments have changed.