No? You can still buy these publisher's games from them if you prefer and, as far as I'm aware, steam doesn't have any stipulations that state once you sell on their platform that you can't do so on others. In fact, that's what these publisher's tried to do. They thought they could easily build their own competing storefronts and reap the money. And, as the article says, they're now crawling back. Turns out, Valve is pretty good at content delivery while remaining relatively consumer friendly.

More people should look up what a monopoly is before hosing everything with that label.

Remind me, which store is paying publishers for exclusivity?

Valve has objectively done far more good in the gaming space than any other company so I would say yes, their achievements are worth celebrating even if it is monopolistic. They've proven to be trustworthy for the time being, unlike other companies.

It's not a monopoly in the way that valve has does bad things to keep it that way, just that every other try has so far failed. Nothing has been close to as good as steam, and probably never will. GOG is good but they're not directly competing in the same way.