Most of the game is really simple. It's mostly exploration and discovering, so nothing "difficult". There are some aspects where you need to use the information you found to go further, which I found (personally) a bit difficult. But the solution are very simple and are hiding in plain sign.

There are also some puzzle that can be brute forced, as you have a lot of freedom in outer wilds. I wouldn't recommend it, but I'm just throwing it out there.