That's the thing: I don't think there is a platform to advertise Steam games. You can get people to wishlist by word of mouth on socials, mail lists, etc.

You can go to events, give interviews, have gameplay footage on streaming sites. You could get lucky and get covered by some big media or a big streamer.

But 'run of the mill' ads? I don't think they'll work for that.

I constantly test this traffic source (Facebook), it’s not always possible to turn the system into a plus, but I can do it! The main thing is to understand the value and what you are selling (the correct geo and the right offer)!