I also finished Mina a couple of days ago. Took me 32 hours, I did do lots of side stuff though. It was a bit difficult at the start due to having to figure out the mechanics, then it got easier because of RPG power creep, and then the stretch towards the final boss is a more difficult again.

It's also difficult to find the path to new areas sometimes.

Overall enjoyed the difficulty, I'd say playing through Mina is about as difficult as getting the basic/bad ending in Hollow Knight (i.e. not counting the more difficult "secret" boss of HK nor the DLC). But unlike that game, Mina has lots of ways to tweak the difficulty.

I recommend Mina wholeheartedly, the basic mechanics are fun and the level design is excellent. Good mix of platforming, combat, exploration and puzzles.

I thought the game was great. It took me less than 20 hours. I am not a completionist. The only thing I make sure to do is to beat all the bosses.

I'd say the game is difficult. It is an old school kind of game. It uses retro graphics, storytelling is quite simple. So it places heavy emphasis on the combat and platforming. The mechanics are tight and responsive so it is a difficult but fair kind of game. I personally found the combat to be easier. The platforming is the difficult part and annoying at times. In this respect it is similar to Shovel Knight, their previous game. But it has a ton of accessibility modifiers to make the game easier or harder.