The graphics of this game aren't that bad. It's just the art direction that's bad, and that's owed to these facts:

1) It's obviously been a rushed game to get Pokemon on the Switch, so it's an easy way to cut corners
2) Kanto's just not a region that pushes hardware to its limit. It's a homogenous, basic looking region, as it should be being the original region.

I wouldn't worry about how the 2019 games look.