I think flying enemies are absolutely terrible to fight, especially early game.

Runbacks are the things everyone has already been talking about. There were two in the whole game that I thought were terrible, so it could have been worse.

However, for boss runbacks especially, because your corpse is in their room, it discourages leaving and coming back later. This can of course lead to just bashing your head against a difficult section and getting frustrated even more. In Hollow Knight your ghost at least spawned in front of the room so you didn't have to commit to fighting the boss, even if you had to make it back there again.

I guess because of how much of the game is optional and non-linear, the devs couldn't often really plan on when players will have which ability or upgrade, so some stuff felt kinda underutilized, for long stretches of the game.

Why are so many shard drops above places, where 75% of them will fall into unrecoverable spots? For rosaries, you at least get the magnet, just add the shards to that or something.