Raised shed floor

Yes they should have been. You might be OK if you put a moisture barrier under them and give them a few coatings of a waterproofing sealer. Since they are not in contact with the ground, you should be OK for a while.

Are the posts on some sort of concrete foundation? If the posts are just sitting on dirt then they will eventually rot and I'd be worried about how much weight they can support. This is particularly an issue given the slope. Even if you don't want to go to the hassle of a foundation it might be worth sitting the posts on concrete pavers or blocks. The other thing I would definitely do is add some diagonal bracing between the posts on the right and the joists to ensure that they can't fold.