Another thing I dislike about "Danny Phantom" is that some of the adults aren't very likable. Whether if it's teachers favoring the popular kids over the unpopular kids or parents being very closed-minded.

This is why I wish there were likable adults in DP. The biggest example being the extremely underrated Principal Ishiyama. She only appeared in a few episodes and wasn't given much character. If it were up to me, I would make her the sort of principal who actually cares about the wellbeing of her students and has a zero tolerance to bullying.

Here's a good example I had in my head for a while:

/////
Dash: (to Danny)
Defacing my letter jacket? That's a violation punishable by wedgie!

Principal Ishimara: (to Dash)
Ahem! And taking your anger out on others a violation punishable by suspension.
/////

Anyway, if the adults in DP were not as unlikable as some of the adults from FOP, we could've had a few more supporting characters.