I am not responding as a coder (I am not), just as a user.
Cache files have the purpose of making sure the application will remain quick and agile in actions and responses.
So disabling it (or even limiting it's size) in my opinion is no option at all.
So I don't think that it is as you call it 'pointless' or 'without demand'.
You want album covers displaying nicely, right?
You want MusicBee responding swift and quickly, right?
Checking my own AppData folder, yes, it is big.
But I think I can blame myself since I have a very large music collection, with high quality album covers. And still MusicBee remains extremely responsive. Great.
So in my case, the AlbumCovers cache folder is indeed large, but the other folders are quite small, since I don't use a lot of "radio, artists, biographies" features. (I believe you are referring to those?)
What are the specific cache folders which sizes bother you?
That might give you a clue what you could probably do yourself in changing usage and settings of MusicBee. (or cleaning up the music files in your library)