The main thing you need for a competent Switch port is a dev team with the right combination of hard work and talent. Saber clearly has that. In fact, I even suspect that hard work is even more important than talent in these situations. A lot of these Switch "bad ports" are really "lazy ports".
The other factor is that we are now at a point in video game history where adding a ton of raw power doesn't give a whole lot more in effective output. It improves graphical capability somewhat, but that is about it. It used to be that new hardware would also enable new and better gameplay and not just better graphics. I don't think Street Fighter 2 could have been ported to the NES without major sacrifices in gameplay, but it runs great on 16-bit consoles. I don't think open world games like GTA3 or Shenmue would have worked on the PS1, but they work great on Generation 6 systems. I even think the giant boss fights in Dark Souls wouldn't work in an earlier generation, because on the PS2 the best we got was Shadow of the Colossus (and those are really not the same thing, gameplay wise).
However, I haven't seen any games yet that have gameplay that wouldn't work on the Switch. Maybe VR games? (But those aren't really popular yet.) As far as non-VR games, the Switch can play all of them without sacrificing gameplay.