In general, I like the concept, but I think the execution is a little lacking. Removing power-ups and replacing them with keys is basically doing the opposite of what Metroidvanias do for games. Also, as has been mentioned before, the shield basically feels like a weapon.
On the other hand, the controls feel decent and the graphics and sound are great. The game feels competently made. I did run into a handful of glitches (dying and restarting causes the music to play over itself a second time; fell off a platform in the chandelier room and it respawned me on top of some brick work where I was effectively stuck).
Solid effort, but a good example that just removing a thing for the sake of simplicity does not always improve an experience.