Wild land does regenerate, but also trees grow, and they have a cost to remove them when they get bigger, especially the roots. Plowing is not possible with tree roots everywhere, though perhaps non-monoculture non-mass-produced crops are possible to grow there and eventually the roots may decay. It can take 20-30 years for roots to decay though, or longer.

Yes and no. Unfortunately it isn't a simple and easy topic which is what makes it so complicated to deal with.

Real thick top soil isn't really the natural state of land in most places, a large bulk of it was grown by the people farming it who spent multiple generations fertilizing it, maintaining it, and putting as much organic waste as they could back into it. It is its own ecosystem that was grown just as the crops above it are grown in higher than natural abundance. In most places it takes 80+ years to build up a significant top soil layer, and in the short term letting the land sit fallow for a bit of time will let some nutrients build up in the soil and will provide larger yields in following years. But if you let it go truly wild, the wild stuff starts growing and is also going to start consuming those nutrients until some sort of balance is achieved between top soil and plants above it. And the natural balance in most places only going to be a few inches of good top soil, not the 1-2 foot of topsoil that maximizes crop yields.

As to over utilizing it, you can both maintain that top soil and get higher yields from it, but if you are willing to push the land a little further and add a little more crop density or not fallow or fertilize the land quite as often, you can push the yields a little higher still. Like pulling a bit of the capital out of your investment account along with the interest payments. You can do that for 10 years, and have more to spend/yield for it, but each time you are spending capital/top soil and reducing yield for following years. Then 10 years in, your interest/yield expectations are lower than ever, so if you want to maintain even the old non-exploitive yield numbers you have to take out even more of it. 10 years again and now you are back to a shitty few inches of top soil. Oh sure, you can try growing it again, but just like capital the less you have to start with the longer it will take to grow, and it took others over an entire lifetime to grow what you spend in just 20 years.

Family farmers didn't usually do that because it would just be fucking over your own kids. But in this modern age, how many farms are actually being passed on to kids? How many people give a shit if the land is dead in 20 years if their plan was to sell out of it at that point? Or if they killed off other local farms by out competing with unsustainable practices that the others refused to emulate, why not buy their good land and run the scam over again? By time any of the shortsightedness of those actions culminates they will either be old and rich with investments into other industries, or dead, and the people who will ultimately suffer for it will just be poor strangers they never cared about and the cause of their plights easily deflected onto other sources.