This wasn't made to help indie developers, this was made to convince gigantic companies to keep releasing their games on steam, and also try to convince companies that never released their F2P games on steam due to the cut profit they would have.
Indie Devs still get the industry standard for every other platform. If the companies want pure profit, they can still release their games with their own website of publisher. It's not like Valve is stopping them from doing that. You go to Valve because they have a gigantic playerbase, and a server infrastructure that cuts down on the costs of development.
A lot of the posts here haven't even bothered to read the post Valve released. For those people in summary:
The value of a large network like Steam has many benefits that are contributed to and shared by all the participants. Finding the right balance to reflect those contributions is a tricky but important factor in a well-functioning network. It's always been apparent that successful games and their large audiences have a material impact on those network effects so making sure Steam recognizes and continues to be an attractive platform for those games is an important goal for all participants in the network.
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Our hope is this change will reward the positive network effects generated by developers of big games, further aligning their interests with Steam and the community.
This is purely in recognition of the big successful games on Steam - Indie and AAA, but obviously much more relating to AAA. These are the games driving Steam's success and in turn exposure to everything else on the store. It is designed to retain those successful devs / pubs. Valve actively encourage devs / pubs to publish elsewhere but always in addition to Steam.