Meanwhile any conversation about Steam’s marketshare - for example an article asking “Can anyone overthrow Steam on PC?” - kinda has to bring this up anyway. It has an impact… and a lot of people will implicitly or explicitly say nuh-uh, at length.
Except, the article doesn't say the word "monopoly" anywhere in it. If you wanted to have a conversation about Steam's market share you could have just mentioned Steam's market share. Then you don't have to worry about other definitions of monopoly. "Steam has a significant portion of the market share" is true regardless, and easily followed with "and that's a concern because..."
But you're not interested in a clearly communicated conversation. You're just arguing semantics and pretending you're making a point.