I sincerely doubt that even if another launcher did everything Steam does, it would rival it. People already use Steam.

At that point, you can start grabbing business from steam via promotions and such. You don't need to rival or outgrow Steam to break into the market, you just need a bit of the market.

And that's assuming they get to this point, ignoring that Steam had decades to get there. It used to be ass.

It's not even that other launchers have less features than Steam. It's just that other than GoG, which has a very limited catalog and no regional pricing, there is not a single store that is not actively anti-consumer to a hilarious extent.