This is true also for steam deck but it’s a success anyway. COD, Fortnite, LoL players can stay on windows. I’m happy to play newest indie game on my Linux machine
Success is relative. The Steam Deck is only unsuccessful if you consider the goal of the device to be "outsell Nintendo". I would argue 4 million units is not merely a success, but a massive success.
The Steam Deck also had no marketing and is not sold in retail stores. It's also been a success in kicking off a whole product category of handheld PCs, of which most games will be bought on Steam.