Is this game too easy?

[Edli]

And what after you finally cleared it? difficult content remains difficult forever

Not a single game remains difficult forever. They're games, they have a set of rules which the player will eventually master. The more you play a game the better you become on it till eventually you understand how everything works inside out. It's actually what makes games appealing. Seeing yourself slowly progress and becoming better at it. Starting as a complete noob, going through hell and being able to beat it after a while without a problem.
Games that remain difficult forever are pvp games, where the opponent is another human which learns at the same rate or faster than you.