Without steam, I'd still be playing my CD version of Homeworld 2.
I have paid $10 for every $1 of game I play, perhaps as high as $100:$1. A 30% cut of that seems totally reasonable. I have hundreds of games I keep just in case, and have played 10s of games I'd never have considered because they dont appear in Game Informer, PC Gamer, GoG, Twitch, Youtube, or other channels. They just are magically brought to me by steam, and I buy it and try it because I'm an adult now.
If game creators hate this, I feel bad for them, but I don't want anything to change as a consumer.
> I have hundreds of games
You do not have hundreds of games. You have a non-transferable license to play those games while they are made available by Valve and while your account is not banned.
Of course 30% seems reasonble to you, you're not the creator of the games. It's quite confusing to me that you're endorsing the side that has an insane ROI instead of the side that is sufferring greatly to make ends meet.