So it means because you disagree you won't change the age rating then or is it more likely a Steam problem? It's not an accusation from my side I'm just curious.
If I understand correctly, I will get the Steam key even if I buy Obscura here?
You should get a Steam key if you get the game through Itch.io, yes. You'll have to connect your Steam and Itch.io accounts (it's in the setting menu), and then on the download page there will be a button for getting a key.
And to clarify: Steam is the one that decided our age rating. We wanted a lower rating.