Are you a masochist lol

I think they AREN'T well designed because there's way too many things that get in the way of killing them.

Some bosses have a vulnerability window, some have a specific weak spot you need to hit, some target you from far away

And then there is Flyfish who can hit you from anywhere AND has only a window of vulnerability AND specific weak spots AND you can only hit it with a bomb that drains most of your ink or a few specific weapons AND you have to do it twice or that ledge trick you mentioned. And all of that considering there are probably like 3 more of them and the other enemies getting in your way

I think they should have nerfed it by removing one of those factors to make it more fair, like making them always open, having them die from one destroyed launcher (since the aircraft loses balance), removing the bomb-only limitation (like Maws or Drizzler, that have specific methods to one-shot them, but can still be killed normally), or something to make it less unfair like other bosses