I don't think they could've done much more with a game having that big of an open world and that art style - very reason why I wrote in that thread after the port was reavealed about going with different art style as better solution (though more expensive), cause inevitably this are results of "simply" downporting it.
Yes, a port cannot be judged on what other games look like on the system. Is the Switch capable of better looking games than this Witcher 3 Port? Probably. Can Witcher 3 on Switch look better? Probably not.
Pointing to other games, that run on completely different engines, and saying they look better doesn't mean that this port could have looked better. It's a port, not a new game, they have to work with what they have.