Leaning shed, should it be straightened or torn down?

I have an old shed on my property that has a lean on the back side of it. The gable ends go east and west and the lean is on the west side and it leans to the north. There is also a big tree on the north side that leans a bit on the peak of the roof. There are decent sized cracks in the foundation as well as some rot along the base plate of the building. You can see some of it in the photos.

Would you tear this down or try to straighten it and fix the foundation and base plate issues?