The only utility Facebook gives me is Messenger, which I have to use because several family members use it. The only utility it offers over other messaging platforms is slightly better support for media and GIFs (maybe?) And network effects. I would really prefer they join me where I am, on Discord, which is where my local friends, neighbors and online friends go to exchange messages. (It doesn't support video sharing as well/easily as Messenger.)
I stopped using Messenger once they started with the ads. Signal is a great replacement. The chat heads on Android were cool but I don’t find I really miss them.
I'm glad you were able to move all of your contacts to Signal! That hasn't worked for me, though many people have joined me on Discord. My siblings are sort of straddling between Messenger and Discord, just like me, but they tend to be more responsive on Messenger. Perhaps they only use Discord to appease me.
I've never enjoyed the chat heads and always disabled them right away. I don't notice ads in Messenger, though I mostly use it from a desktop browser with uBlock Origin enabled!
But as a I said, I only use Messenger because I have to, as it is the primary messaging service family members tend to stick to.