Yes, ‘My Posts’ is the equivalent of how it was - ‘Activity’ (in your profile shortcut) shows EVERY post, not just threads like ‘My Posts’ - the lesser of two evils, to be sure, is to keep My Posts as it is, showing the threads one participates in, and for those you have to dig out to post in again (so they again show in My Posts, but as threads, as everyone likes it) you can use Activity or search to find, as you can even search for yourself and terms you’ve used. Once you post in there again, you ‘refresh’ your My Posts list - won’t take long for most, I’m sure, as it is unlikely many want threads they last participated in 10 years ago in that list - they want the more recent ones.
I changed it back to My Posts as it was, because this way we have BOTH options - My Posts (which will continue to populate as you participate) and ‘Activity’ which gives every single thing you’ve done, every post, reply, etc - best of both.