There are many I can think of.
First of all the issue is not the homo economicus it self but how it is interpreted.
Humans are homo economicus (rational selfish), in a sense that stones are stonyeconomicus with the additive inverse of potential function as utility function.
The theory that stones want to minimize it’s potential energy correctly predict stones behavior on free fall and slippery slopes. The problem is that it’s simply not true. Stones do not have a will, let alone rational. If you interview Mr. stones, do you really rationally want to lower your potential energy, the stones don’t know. “Potential what?”