Personally, I wouldn't call this game boss-fights-focused. Atmospheric exploration and story were a focus just as much as boss fights. But not everyone likes walking simulators and story games, I suppose.

Either way, yes, this game is on the easier side. I'm far from a Danmaku god, and I hate being stuck on the same boss for hours, but I still thought this game should have been harder. It has accessibility features that make the game easier, but it feels like it should also have unaccessibility features that make the game harder. I guess we can already not use the second half of health bar, which would be basically doubled enemy damage, but that's boring. Using only the revolver is a better idea, but again it's a bit boring. Length of a battle and low damage of your weapon shouldn't be the reason the battle is hard. Ideally, bullet patterns and other boss attacks should have been harder, and people who have problem with that could use accessibility features.

As it is, I recommend avoiding Inner Beast upgrades for a non-boring way to make the game harder. I did my first playthrough this way, it still was easy, but at least a bit harder, and it didn't feel as boring as using only the revolver. Another thing I think could be a good idea is to avoid using dodge roll, or at least use it sparingly. It probably should have been limited to a few uses, and then you need to wait a bit to use it again. That's one way to make dodge less OP that I saw in another game, maybe there's an even better way. I should a try a playthrough without dodge roll at some point, it could be fun indeed. A noob like me would probably fail to pass the game at all this way, especially without Inner Beast's OP Spirit Blast and invulnerability. And last but not least, I wonder if it's even possible to beat the game using only the sword. Could be fun...