So this game is fun, has nice exploration, fine combat, dark fantasy vibes.

It just can't really be called a Metroidvania. If you enter a game looking for something and it never shows up it can sour an expirence.
Outside of non linearity, the one thing that actually makes a Metroidvania a Metroidvania is power up progression. Blasphemous does not have this. It's a non linear action platformer with no power up progression at all, making it more like a 2D Dark Souls than a Metroidvania. I've heard the 2nd one does much much better at this and I'm very excited about it