Thats how it looks on the Switch itself. Different time of day/weather i think tho.
Dont have a problem with it, overall it looks fine, and seems to run mostly fine.
To me it will always be a matter of taste. I like the artstyle direction Legends Arceus went for, that kind of high contrast style to make it look like those old paintings, including the odd shape of the trees, and the thin strands of grass that don't cover the entire area. My main complaint is the base of the grass having that leaf-y pattern/texture instead of being solid shades of green.
I still believe the Pokémon franchise would be better off if they aimed for a cartoon-ish, fantasy style, with solid color surfaces, rather than wanting to do a more realistic approach, and failing in the attempt. Mainly because the Pokémon creatures and the human characters look better with that cartoon/anime style than having realistic features, like Pokken or Super Smash do, like making Lucario hairy, etc. So even if they went for this magnificent graphics people want, the clash between that and the Pokémon creatures would be just ugly.
In general, not just Pokémon, but even looking at screenshots of BotW, etc, I don't remember a game where surfaces like rocks or mountains look good, as in a realistic kind of way. So I always feel like a more cartoony style, like that of the new Spyro or Crash Bandicoot games, would fit most of the Nintendo franchises, including Pokémon.