While being federated is a huge plus for me, it still needs to be a good and usable messenger on all other fronts. If I can't imagine my mother using it, you are doing something wrong.
I am not usually of the "software must be usable by a baby"-front, but for a messenger adoption is key, and unless I only talk to my nerd friends it needs to be both simple and at least up to task with Signal (videocalls, groups, easy to find contacts, ...)