Yeah, there were a lot of myths invented to try and discredit the Wii's success.
The "people bought only bought it for Wii Sports/Fit, played for a weekend, then never touched it again" is one of the most absurd. According to Nintendo's own internal data, the Wii has a software to hardware ratio of 9:1, so on average a Wii owner had 9 games for it. It's attach ratio is actually higher than the N64, which was 7:1.
So the average Wii owner bought more games than the average N64 owner.
I hadn’t heard about the attach ratio being THAT high, but yeah...it’s not like Wii software didn’t sell. Mario Kart Wii, New Super Mario Bros, and Wii Sports Resort remain some of the best selling games, period.
And on top of that, the Wii remained the top selling console for most of its life. It did peak early, but something that was a top selling console for four years and sold over 100 million in six was hardly a “fad”.