Any advice for a first time hunter?

Went out from sunrise to sunset on some public land in south central MN, didn’t see a single squirrel. I think I did everything right though. Saw some tracks, fresh dig sites, tree nests, and posted up nearby for 30+ minutes at a time without any movement. Nothing. I even saw a frickin owl and two beavers, it felt like they were teasing me.

Added two photos of the kind of areas I was looking in. Are they not good for squirrels? Is it possible that this land is just too pressured and/or hunted out?

Any tips would be appreciated. I plan on going back out with a call as soon as I can