Are you kvetching because the most direct possible answer was only the second thing I said? Not counting where I personally explained it to you personally an entire year ago.
After the more recent clarification, you made clear you still thought monopoly meant illegal. "Everyone calling Steam a monopoly is implying that." My response was "The point of acknowledging Steam’s monopoly is recognizing things could go bad."
Now Steam is no longer a Monopoly in the legal sense, are you no longer concerned about the amount of power Steam has?
I'd be massively less concerned. A game off Steam, but on all those competitors, would still be seen by the majority of customers. Those competitors have motivation toward pro-consumer intercompatibility. Customers have a choice based on whatever they consider important - like user interface. Publishers would care about percentages, because the choice is not between giving Valve their pound of flesh, or an anticipated sequel taking two years to break even.
Basically it turns out competition is kind of important for capitalism? The cases where a monopoly works out better are rare... and fragile.