But why would you expect that though. I'd think that if there's a generic protag in almost every single harem series that people would eventually stop expecting it, but I guess not.
Bro, I'm just trying to explain to you why I (and others) don't like that series (or many harem series). I don't have any inherent problems with the idea of harems (or whatever love polygon you want to use) or monster girls and I'm certainly not one to get all flustered over tig ol anime bitties (I've enjoyed a lot of anime with a lot of fanservice). However, I need substance not just frosting. Otherwise, all you're consuming is empty calories and that's stuff I have no real interest in having in my diet.
These shows are just about tits and lewd shit. Anyone who complains about character shit in a show like this come off as tryhards who like to be negative about things.
This is a false dichotomy you're setting up. YOU CAN HAVE BOTH. Prison School and Monster Musmue are both decidedly smut. However, I think Prison School is actively good and I think Monster Musume is actively bad.
Prison School has:
-Distinct characters with defined and multi-layered personalities that undergo actual character development (like almost the entire cast)
-Quality character interactions (Kiyoshi and Gakuto broship, Mari and Kate rivalry, etc.)
-Comedy that actually works and uses the absurd expertly (Too many examples to list)
-Excellent and striking art (Just fucking look at it O_O)
Monster Musume has:
-Static characters that can often be described with a sentence
-A main protagonist with no interesting attributes
-Flat and sometimes straight creepy comedy
-You can find better, more unique art and character designs if you spend 5 minutes on tumblr or deviantart
Like just because they are both smut doesn't mean there aren't tiers of smut or that they are above critique.