I can see your point, but Infuse is also much more than just a client for Plex. There are certainly cases where someone may have Infuse connected to a single Plex server, but there are also users who have 1 Plex server, 3 Emby servers and 2 SMB servers. The Apple profile option provides more versatility to cover these kinds of cases.
There could be future changes geared specifically towards deepening the integration with Plex profiles like you described, but I think we can consider that a separate item.