You are walking and see a very high place, that you can't reach with your basic jump, so you decide to continue on your way.
Eventually, you get the power of flight. Your mind goes back to that high place, "oh shit, now I can get there and see what's in that place!".
Multiply that several times, with several paths, with different powers/gadgets/abilities/whatever, and that's Metroidvania.

The nature of the obstacles and the tools that unlock those obstacles doesn't matter, if the world is structured around blocked paths and tools that unlock them in non-linear ways, that's Metroidvania or at least Metroidvania-adjacent.