My dad built a "dog house" (we use it now as a shed) 25 or so years ago. My parents have been divorced for 22ish years now?

The original floor has rotted out. My Mom put new plywood on top of the old stuff (I know, I know) and due to the moisture from below AND a hole in the roof from a tree falling last fall, the NEW floor has rotted out.

I was wondering: before we replace the floor for the 3rd time, can we pour concrete under the shed WITHOUT trying to move the stupid thing? That would prevent moisture from the bottom rotting out the floorboards -- and prevent any more damage to the 2x4s that are supposed to be supporting the floor. Right?

Or am I completely out of my depth and we should burn it down and built something new 😂🤣