im the exact opposite. i only buy on steam and never on itch. you should download steam because they have great features and are doing virus checks and testing before each game is released to the public. on itch there are a lot of games that contain malicious code in them.
I buy from GOG, Itch.io and off of developers website through Humble Bundle my current living situation along with Steam's lack of support is a pass for me . I have never had trouble with viruses on itch.io but I definitely understand. I'm at The point that if a game isn't available on a platform I shop at they obviously are doing so well they don't need my money.