Not sure if you can draw that conclusion yet. The deck has been perpetually sold out since launch and is still a 6 month wait to get a device, they are selling them faster than they make them at the moment.
I don’t think this product will ever compete against the broad marketing effort of Nintendo however, it’s sort of a niche product in the end. With that said the comparison itself is odd.
Full disclosure: I do NOT own a deck and I do not intend to buy one.
I also see it as the two products also focus on different areas. The steam deck is going to appeal to the more graphic game crowd (as in something like Dyling Light), probably older audience. Even though Nintendo has release some of their restraints on M-rated games and such, Nintendo still markets to a younger crowd that graphic games don't appeal to. Sure there are games designed for a younger or more light hearted crowd on Steam, but Nintendo still dominates this space and probably will continue to. The steam has the ability to emerge a new market in hand held gaming for darker games and such, such as Elden Ring. My guess is the overlap between the Pokemon/AnimalCrossing/Zelda crowd with the Elden Ring /Metro Exodus/DyingLight crowd is not huge.
Some more nuance, there are also older people who enjoy the switch to. I am 28 playing the switch, Zelda games always have a special place in my heart for me.
I also don't see much competition of Nintendo Switch vs Steam Desk. I see the Steam Deck mostly competing directly with Gaming PC and Console gaming (xbox/playstation).
I don’t think this product will ever compete against the broad marketing effort of Nintendo however, it’s sort of a niche product in the end. With that said the comparison itself is odd.
Full disclosure: I do NOT own a deck and I do not intend to buy one.