Multi Monitor support on a remote session for one. In fact as of right now the situation is even worse and causes the application to crash altogether instead of dropping back to a single screen. Yes, I probably could force a x11 backend and it might work. But I shouldnt have to.
I am assuming this is the same security issue that has been there for a while. So many applications that could interact with other screens become broken. Maybe some of that is fixed, I suppose I should try again. But until I can multi-monitor with a remote session, I don't bother trying.
xfce is really not an important project IMHO, it's an interface from the 00's that doesn't have a clear usecase to me at all. It's a strictly worse version of KDE in my eyes. The only reason to use it seems to be if you're already used to it and don't want to have to change anything.