That is not true if you factor out all the people developing games independently on their own dime, against better financial advice. To counteract that, there just aren't enough developers working on enterprise Java architecture for no money, out of passion.
It's also only fair that people who get to work on "fun" things like games are paid less. If they don't think it's fun, they can switch industries and earn more. Nobody is doomed to be a game developer.
> I'm not arguing against any change, it just seems spiteful that Valve are sticking it to the little guys who can't go anywhere else.
The little guys can go to itch.io, which charges as low as 0% commission. They may even have more visibility on there than on Steam, given that it's a smaller pond. There's also the Humble Store, which leaves commission up to the buyer.
> This could have been a great chance to improve Steam overall, by reducing the commissions for all developers...
They did reduce commissions for everyone by 5%. The extra 5% is for those who are at risk of moving off the platform because they can create their own visibility.