Some understandable criticism based on expectations from the original idea they had.
Valheim is a colorful game overall however, and that was one thing that felt out of place was the drab and dark of Mistlands' original concept.

It was probably reconsidered behind the scenes to match the rest of the game's play on colors and thus why they went more vibrant. Only part of the game that doesn't feel colorful is mountains from what I remember, but even the swamps have splashes of color. Surtling fires, many different hues of browns, greens and blacks, purple leeches, etc.

I can't comment on it's similarity to meadows as I've only seen the trailer. It looks more like a place that might have once been meadowish but is overgrown and forgotten whilst steeped in magic/power.

Lastly, spiders (the webs) were probably reconsidered due to many people's arachnophobia. I was interested to fight the creepy eight legged critters, but I understand their not following through on that one as an enemy.

EDIT: Figured I should add an example of color, it's often done through reflections and the ambience as well as direct color of the environment https://steamcommunity.com/sharedfiles/filedetails/?id=2514856379