It outsold all expectations and was successful enough that it brought several traditional PC makes (Asus and Lenovo) into the market.
It's obviously sold less than established consoles, but it's done well for itself. Also even though it's a small percentage of steam users, it seems to represent some of the more active players/spenders on steam. Thanks to that, steam deck players seem to be an actually significant percentage of steam sales for many games despite the lower number of steam deck players.
Oh yeah it did, they weren't going for mass adoption, but there was a niche market that needed it and they filled it. Preorders took a year to produce. Being successful and profitable didn't use to mean literally every person needed to own one
The article you've linked seems to say the opposite of what you're suggesting — that a second iteration of the Steam Deck is coming soon. That's not the impression I get from the linked article at all.
But even that aside, I would argue that the Steam Deck has been uniquely successful. Sure, the Deck may or may not end up being a "one and done", flash in the pan piece of hardware that fades into relative obscurity in the face of competing hardware... but it proved that the idea of portable PC gaming was possible and affordable, and inspired plenty of manufacturers to dip their toe in the same arena. And almost every single one of those devices, whether it's sold by Valve or Lenovo or whoever, will be running — and selling games on — the Steam marketplace.
That was the goal of the Deck, and in that regard it's been a great success.
Well seeing as there are a billion accounts and 120M active users, that's a LOT of decks sold. Numbers online saying 1.2M decks sold which is a lot for a niche PC handheld. There's already copycats.
I think suggesting that Valve need any given game (CoD) or even genre ("games like CoD") to remain successful is silly at best. Of course Steam, the Steam Deck, and as a result Valve are only successful or even exist at all because of video game studios and publishers. But Call of Duty specifically? Nah man, it's a blip on the radar for Steam.
While I disagree with your core argument about the success of the Steam Deck, I absolutely agree that I'd love to see a desktop variant of SteamOS become available for general use. To the point that I'd likely even finally make the leap from Windows.
Wouldn't that be several million units with the size of Steam's userbase? Of course established consoles are more successful but that doesn't sound like a terrible start, especially for a handheld.