Steam was that way for a very long time, and the bodies of it's various issues are what it's currently built upon. Companies should just get on the Steam train, take advantage of that platform and stop trying to invent a new Steam.
One day Valve will stumble, but I don't think that the spoils will go to one of those who made fools of themselves while Valve didn't.
Ambition is a hindrance to trust, that's why from the current crop, the only plausible candidate for a Steam successor is GoG. They give a believable impression of keeping up their business as long as they at least keep a certain niche of the market, while everything else looks like projects of the "displace Steam within x years or be shelved" kind.
Steam has been a godsend to indie developers. It can be a great partner for AAA ones as well.