To all those people complaining, you try to make a game, see how far you get. Multiple games on Itch.io have been released on Steam and the devs of those games do not provide you with keys for Steam if you purchased it here, stop complaining. This game is cheaper than a Mcchicken even if you buy it on both platforms. Buy the game again so you can support the dev so they can continuously update the game or make more games. Making anything creatively is very time-consuming and Game Dev is twice that time, especially if you're a single person.
Let's not be dishonest, you literally went "try and make a game and see how hard it is" and "game dev is time-consuming and hard" which is true, but you're using that as an argument against people complaining (having an opinion) on the handling of the itch.io version vs the steam version. People are allowed to express frustration without needing to experience the woes of game dev first hand.