Does anyone think otherwise?
I don't, and think Switch has enough power to do most things it wants to do (though we've seen plenty of games that show its limits, and a Switch Pro would be really nice for those who are getting enough gameplay out of the machine but not happy with blurry graphics sometimes) ... but the counterpoint would be the Wii.
The original Wii was a phenomenally successful gaming system, but the software for it dried up too soon for a platform of such dominance. (Whether that was an overabundance of shovelware, or just a disinterest in core gamers with its visual performance, or even a sated satisfaction with the AAA Nintendo games which succeeded but left no room for the As and Bs from 3rd Parties, I"m not sure what the general analysis of the Wii's time is.) Big brands outside of Nintendo products just rarely translated to any success on Wii; most AAA 3rd Parties avoided the system for the higher-spec platforms, the few ports of big games that did come over were increasingly disappointing as conversions as the HD platforms gained steam and sped away, and the few attempts at bringing over blockbuster brands in Wii-formated style like NFS Nitro and RE: Umbrella Chronicles didn't generate anywhere near the same heat. For a lot of people, Wii just became their "Smash Bros Machine", or it was their party device that they'd dust off for Wii Sports and Guitar Hero, or it became the way your grandmas got their Netflix. Everybody had one, but it was nobody's go-to gaming system except for Nintendo's top games. A system that has units moving consistently but then can't move software besides the annual Mario game, I'm not sure I'd consider it "still thriving."
...I don't personally see Switch following suit, as it's in a different situation thanks to its blessed portability, but DS had a similar hot-then-cold run (once it recovered from a weak launch and became one of the best-selling gaming platforms of all time) of the market. The success of the Switch by no means promises a smooth road ahead; Nintendo and its partnered developers are going to have to fight hard to keep this system going strong.