The chopping is really satisfying but the upgrade tree isn't that fun. There's no reason for the tiers to be there. It becomes a bit tedious to get all the tiers and not worth it to read the descriptions because of how often you are buying upgrades. Just give us one big upgrade instead, or at most 2 big tiers per upgrade. That way getting the upgrade feels like a milestone.
Would also be nice if there was any actual difference between the trees instead of just recolors. For instance medium trees being chopped down in phases, first the branches then the trunk.
Finally, "The Forest" gives so little wood that it's not worth investing in. If you want to give us passive income it would be more satisfying to have something on the main screen. Like an infinite tree on the side of the island that is being chopped by an automatic axe and you see logs flying to your pile.
Overall a fun game with a strong start that left me a bit disappointed with its progression.