No, the Switch sold hugely on its gimmick of being a portable ''Home''-Console.
If that was true then the Switch Lite would've bombed. It's like saying it sold on HD Rumble, a neat feature but it's Breath of the Wild that sold the system more than anything.
Did it help, sure. But it wouldn't matter to people if you could play a home console on the go or not if it wasn't for compelling software, which BotW absolutely (somehow) was to people.
Again no, I don't think that Namco would have been able to improve the graphics of Soul Calibur much on the Dreamcast.
This is just intuitively wrong. Anybody who's been gaming long enough knows early titles usually don't look as good as games released near the end of a console's lifespan, and that sequels usually look better than their predecessors.
If Dreamcast had a normal lifespan it goes without saying that a launch game's sequel nearly half a decade later would look noticeably better. It's technically no guarantee, but that's how things typically worked at least through 7th gen.
I nowadays believe that Sega's only chance would have been to scrap the November 1998 release of the DC in Japan and instead release the DC in December 1998 in America.
Releasing a successor so soon at all was a mistake, let alone sooner. They wasted money fucking up with 32x and Saturn, they should've rode it out instead of relying on a hail Mary with an early Dreamcast release. I get why they did it, but it obviously didn't work.
If they waited longer then they could've had an even better launch line-up (DC's was already arguably the best), had more online games ready sooner, perhaps more feasibly included DVD, and generally improve the console (beef it up a bit, fix their controller, etc).