I think this is a case where the Lemmy features and client just aren't there yet. It's improving fast, but it's not going to catch up to 15y of reddit development overnight.
As to how I handle these things:
- Mostly I browse by new and don't excessively revisit posts/comment-threads.
- If there's something I really want to dig into but I'm not ready yet, I save it. I only do this a couple times a week, like for example I regularly do it with https://lemmy.ml/c/formula1 race threads if I haven't watched the race yet and don't want spoilers.
- If I want to revisit a post/thread as it develops, I'll scroll back through my recent comment history to find it. If a post really takes off and has more than 50-75 comments, I get lost anyway and have trouble finding new stuff... though sorting by new helps find top-level comments at least.
None of this is fancy or sophisticated, but it works well enough for me.