Got it on PS5. 3 levels in and I think it's really good. This is what I wanted Mega Man 11 to be, basically.
Saw reviews say maybe it felt too old, but I think it feels super modern. The jump elasticity and air steering precision is higher than a modern Mario game, and the checkpoints are super generous compared to plenty of 2D action games.
So far bosses go down easy once you learn the pattern (though I wouldn't even be impressed if someone took them down on their first try, just because they're not too oppressive).
Level design is good too. Only complaint so far is maybe they used those hovering bug guys just a tad too much in level 2, for that castlevania-like knock back death, but you can just jump at them and it'll push you back onto your platform, let alone they only charge at you twice before leaving the game entirely without respawning.
To anyone being afraid of this being like Ninja Gaiden too much: it's not. There's no eternal stream of enemies, and most enemies not only move much slower, but have much fairer patterns/angles as well. If anything, this game is like a mega man game, that just so happens to star a ninja.
Enemy placement is actually a thing, and it's thought out, unlike those older games where they just kept chucking them at you, without necessary having them be in any specific location on screen, to save memory and to keep you from sitting still.
EDIT: Serious noob question: If my TV doesn't support 120hz, is the game still 120fps on PS5?
Game feels perfect, so I don't mind if it's not, but I'm curious if anyone knows how it works.