I mean you technically kind of can. You just collapse the username@domain entry after adding the ones you want to the favorites, then you only have the folders you want to show in the favorites section without all the noise there.
Archive, Scheduled, Conversation history, Filer_Snooze and Clutter are all created when you use a related service. I.e Archive is created when you right click a message and choose the Archive option. All other folders are standard. My point is that all the folders in your screenshot exist because a related service is actively being used or had been in the past.