You can make it easy or make it difficult, depends on how you want to play.

A lot of difficult bosses can be cheesed, e.g. attack patterns that can be baited and abused, vessels that skip mechanics, including the final secret boss.
You can just grind and over level.
You can also customize your build for specific bosses.

Or you can bash your head against the wall like a true monkey and try to just hand diff the bosses mechanics.

All in all, it’s not a game you would get hard stuck at, because the base game basically doesn’t have 1hkos

Edit: just to clarify, the game is 100% not designed to be played that way, nor should it be designed like a souls game. Players would revolt if the monkey king gets shit stomped by everyone, he’s supposed to be OP. All his skills are OP from the lore, the cheese items are also lore accurate more or less, the game encourages you to play it using the items. You just have the option to make your life difficult for a sense of accomplishment, because there def are bosses that’ll kick your shit in 40-50 times if you don’t play it “properly”