The biggest thing I lost in a similar switch was ANY old conversation with somebody who was an iMessage user. Where they reply to a conversation and think they are just texting you, but actually they are sending iMessages that you just aren’t receiving. Especially on, for example, family group texts, people just find the old conversation and continue it from the previous year or whatever. Lots of times when I was on windows phone or had iMessage switched off, I’d only get the parts of the conversation coming from non-iMessage users. A good example is random family members who use android texting me reactions to an original text or picture I didn’t get. It’s really dumb. Maybe there’s something I could have done about it in my own settings, but instead I ended up switching back to iPhone recently. Not just for that reason but it sure was nice to get messages properly again. But also more sensitive stuff like somebody sharing pictures of items related to planning a funeral.