I really don't think a potential Rebirth port would sell poorly on Switch 2.
We've seen third party ports like Hogwarts Legacy or Witcher 3 sell well enough on the current Switch, and the Switch audience is big on JRPGs; Dragon Quest 11 sold more in its first week on Switch in Japan than Rebirth did on PS5, and that's despite the Switch version being two years late.

Why are you clinging to Dragon's Dogma as if that means anything, it's not even the same team or even a related franchise to Monster Hunter, and DD likely has nothing to do with actual technical capability, it's just a poorly coded game, plain and simple. Don't tell me it's doing anything revolutionary with its CPU usage, it's just optimized poorly probably in part because Capcom didn't give it big enough of a budget (it's a B/C-tier franchise), there's no big mystery going on there. 

The MH Wilds decision has nothing to do with CPUs or GPUs and likely has everything to do with 8 million people on Switch buying MH Rise. That sold way too well for a spin-off, when a spin-off sells as well as any of the other mainline home console versions, well people in the business department start asking questions like "why the fuck is XBox our second console again?". It's clear there's a massive MH fanbase on Switch. For your sake, MH Rise on Switch needed to sell like only 2-2.5 million copies max. It destroyed that and sold like a main line entry as well as World did on PS4. 

Yeah World does NOT look like a Switch game. It's not among the very best looking PS4 games but it's clearly a PS4/XBO title

Assuming the S2 does well.  Don't get me wrong I think the S2 is setup for success but people seem to think it is guaranteed to be a home run out of the gates.  People thought the same with the ps3 based on the ps2....