I don't entirely disagree, nor did I mean to imply that smartphones alone were the reason this won't do Wii Fit numbers. The success of Wii Sports and Wii Fit will never be replicated IMO because they're like that joke that's only funny the first time; the exploded due to their novelty and freshness, but now that it's been done, it'll never be novel and fresh again.

I can agree on that, the novelty of it was a factor. Not sure how much that makes, I still think half of that number is possible. What I disagree with is that Smartphones replaced the Wii successes.

Labo was more geared for kids, this here is 100% geared to adults. LABO was hard to understand for the general public, but I doubt this here really will. I mean, what part of fitness is hard to understand this time around?

While I don't expect Wii Fit sales numbers, I do think it will do quite a bit better than Labo did. 3M+ LT is my absolute minimum prediction, but I expect quite a bit more, more like 8-10M.

Speaking of Labo, the Varieté kit is down to $40 on Amazon right now...

Hey now...  There are plenty of fat kids out there.   Don't forget about the fat kids!

Well, I expect more that parents buy it for them than that they buy it for themselves, unless we're talking about late teens (16 years+), which I counted towards adults. But I agree that Ring Fit has a rather wide market for itself.

I actually think people are underestimating how attractive that feature will be.  It's not that people necessarily care about the adventure, but I think they'll understand the value of a feature that motivates you to keep playing.  I think the product on its face will be very appealing to casual gamers, I just think the price is the main barrier since this is essentially a 380 dollar investment if you don't have a switch in the home.  

"The X audience has disappeared"
People could easily have said this about Super Mario Bros or 2D fighting games after the SNES. It's bullshit.
Good games don't die unless the gameplay is upgraded or sidegraded. Eg Goldeneye - Halo - CoD - Fortnite. They just take a break.
I never played Wii Fit, Guitar Hero or Dance Dance Revolution but the idea that only 90s kids or naughty casuals can enjoy these games is silly. Same with the idea that "they've gone to smartphones". It's like saying the 30-40m Super Mario Bros fans are all playing Super Mario Run. The numbers might agree but reality doesn't.
New Super Mario Bros on Wii/DS outsold all other 2D mario's combined yet it was considered dead for nearly 2 decades.

When Mario Kart's sales dropped 80% between Wii and WiiU, did anyone claim the 'Mario Kart audience' has moved to mobiles?
Of course not because it's only the cazualz who are fickle even though 'they' were the only ones still playing Wii post 2010 (Just Dance).

Will a Wii Fit port sell 20M+ like the Mario Kart 8 port did? No probably not but that's because cazualz want new/improved just as much, if not more, than Mario Kart fans.

Re:Malstrom.
-NES and GB were port central. Handhelds always are. Wii wasn't short of 'PS2 waggle ports' either. He's right that Nintendo could be delivering Switch Fit/Sports now instead of 3-5yrs from now but what better way is there to make a new 'Switch Sports' than to test gameplay ideas through ARMS and Mario Tennis first. Other IPs improve through competition but Nintendo is in a unique position where no-one attempts to/can compete with them anymore so they have to compete with themselves.
-Kinect Adventures sold 25m. ~$3Billion in revenue. What's his point?

I think you're going to be very disappointed if you're expecting 8-10M in sales. 

People have already been there/done that with the "try and get fit with video games and some plastic shit!" fad of 10 years ago. 

This will be on clearance at $40 on Amazon probably at some point itself too. 

Super Mario Bros. is a pretty singular example, you're probably talking about the most famous video game series in history. You're can't use that as a barometer for everything and NSMB was inexplicably also the first new 2D Mario game actually starring Mario since 1992. So about 14 years in between. 

Most 2D platformers don't do massive business these days. 

Wii Fit U flopped just a few years back, Mario Kart 8 is the best selling game on the Wii U I believe by a large margin, it's just limited by a tiny userbase. Wii U sold about 13 million consoles and MK8 sold like 8.5 million copies, meaning the attach ratio there is insanely high. 

No small wonder if nobody makes them anymore out of the big companies except Nintendo. And just look how successful the indies are: Shovel Knight, Shantae (though that one has shades of Metroidvania as well) are pretty big sellers for indie titles.

Wii Fit U flopped since everybody thought the Wii U was just a tablet add-on of the Wii and way overpriced for that. Casuals continued to buy the Wii for their fitness instead. Iirc Wii Fit Plus still sold on par to Wii Fit U the year the latter got released, and the Wii was long dead already by that point.