Not sure what you're getting at. Even if we go with your number, for many people, the 10 games they'll play will be different, which is where the wide selection comes in.
Also, just because there are low quality games on Steam, doesn't mean that there are less high quality games on it that on the Switch. I'd be very interested in numbers to back a claim that there are more high quality games on the Switch than on the Steam Deck.
Also, how do you know Nintendo has a higher bar for quality? Could it be that there are less game developers for the Switch than for Steam?
Huh? I have basically only used my steam deck while traveling, and I don't travel that often, and I've played easily 30+ games on there. There are thousands of games that are excellent on the hardware, I have no idea what you're talking about.
Most Switch owners won't play more than a handful of games, because every Nintendo game is priced at $60 in perpetuity.
That's fair. I've checked out some games, but I haven't actually got started on any yet. I've had a switch in the past, I maybe played 7-8 games on it.