You can continue to exist for eternity without growing.

Object can, life can’t. Life is the subject matter.

A stone doesn’t grow, neither does a forest necessarily even though the trees do until they die. So each tree grows but not for eternity, and the forest doesn’t grow but exists (potentially) for eternity.

Yes.

Capitalism would want the tree to grow eternity.

No. Capitalism wants to grow from the limited resources of the tree for eternity.

Just like cancer wants to grow from the limited resources in your body for eternity.

Just like life wants to grow from the universes limited resources until eternity.

All inevitably unsustainable.