> The combat in the original is really bad/way too easy, and the exploration is just okay

Personally I find combat to be one of the less important aspects of Metroidvanias. I prefer the main source of difficulty coming from platforming around environmental hazards.

I felt like exploration in Hollow Knight was a bit too broad, and lead to too much unnecessary backtracking. Backtracking is a balance. It's a staple of Metroidvanias, but if the backtracking search space is large enough and places aren't distinctive enough then the search for a previously insurmountable obstacle can start feeling like looking for a needle in a haystack. That was my experience in Hollow Knight, and something I felt like the first Ori game did better.