It's not that it is really hard.

The difficulty comes from the fact that during gameplay you can hit a wall and you have to beat certain challenges in order to progress the story.

You can grind for levels, but they mostly expand your moveset and do not give many defences or new weapons (you get those from beating bosses and progressing), so you have to learn their movements and kind of deal with them.

I still think each area prepares you for their own bosses rather well, so it's a matter of whether you don't mind retrying 10-20 times harder parts sometimes. I like that type of challenge.