Animes and their seasons.

An immediate problem with this would be scoring. Say you loved the first season of a show but the second didn't do much for you. If they were listed like this, you'd either have to lower the score and underrate the parts you loved, or leave the score high and give unjust praise to later parts.

Also, there's sometimes a change in director/studio etc. between some seasons, making it hard to put them together into a single "database entry".

Then again, it also brings the question of why does shows like My Hero Academia have multiple season entries while others like One Piece, Naruto, Bleach have only one. With the different arcs and everything, it would make sense to have more entries for those shows even though I do assume it would create more work for the staff to backtrack all of those long-running anime...

I've thought about this too, but it's just much more effort than it's worth while bigger problems still exist.

A decent alternative I thought of was to let users create custom groups of titles and have them appear as one entry on your list that you could give a score to and write notes for, etc. Still not something I would give a high priority to though, as I said there are bigger problems.

Anime seasons are much more different than the seasons of a regular show. Take Ashita no Joe for example, there is a 10 year gap between them and the first arc of season 2 is basically a remake of the last 2 arcs of season 1, not to mention the change in studio.
Anime isn't really planned out like regular shows, they pretty much just decide "we're going to adapt from Chapter X to Chapter Y" and go for it.

Ashita no Joe
Ashita no Joe 2

Being able to list anime series rather than anime seasons, is for me an essential feature, more so than ratings. Without this feature I might as well use trello or OneNote.

Ideally I should be able to add an anime series to my list and have the seasons (and movies, and remakes) as sections or tabs on the series page.

I want to add My Hero Academia, not Season 1 and Season 2 and Season 3 and Season 4 of My Hero Academia.

Despite replies above, I think unconventional seasons are a reason to have a series overview, not a reason to not have one. They are related and have a shared history, an understanding of which will give you a better understanding of all parts.

You don't need to do away with season or their ratings, to add series. You could even have a global series rating, and a local season rating which takes precedence.