I actually think early game chopping is somewhat fairly balanced. 30-40 production now, vs lots of turns with +1 production from a forest is actually a pretty tough tradeoff. But the biggest problem is that the later you get in the game, the more the tradeoff doesn't make sense. Now in the late game you get 150 cogs now, when you might only have 40 turns left in the game or less. There is absolutely no reason to not clearcut everything in the late game, no reason to not harvest every wheat tile to get population boosts, etc... It makes some ridiculous things like the best city to build a spaceport as some random city in the middle of an untouched forest, since you can just chop all the trees to launch your spaceship.
I think they need to do a few things:
-Decrease the chop yields as you move later. So instead of keeping it so that chopping 1 tree = 1/3 of a district, have that ratio drop as you move later. Maybe it starts as 1/3, but by the end a chop is only 1/10 of a district
-Increase forest yields as you get later. Not just lumbermill yields, but forests themselves. Maybe stuff like having a research lab give you 1 science on each forest tile in the city? Or when you get conservation, instead of just +1 appeal for old-growth, you also gain culture or faith from forests? Basically, they need to do more to make you want to keep forests
-And most importantly, they really need some sort of global penalty for chopping. Civ 4 had the great mechanism of forests helping with health. And while it doesn't make sense to have them provide housing, if they could have some sort of late-game "pollution" mechanism, then forests would be a natural anti-pollution mechanism. So late game maybe you can chop the forests for an immediate yield, but that will lead to increased pollution