For first timers, sekiro will feel like a bad joke. It's brutal, it's hard, the learning curve ⤵ is steep and everyone else needs just 3 hits to kill you. For Boses it could be as little as 1.
After a while you understand the basics : Deflect, block, counter and forget about Hp. Stick to posture damage and you'll be fine.
The only downside to the game is that after a while everything is so predictable it becomes boring except Ishin of course.
Five stars is a bit excessive but 4 doesn't really express the terror of the demon of death. 4.3 would be about right