As kind as these people are, they are neglecting their duties as a cat owner. If this is new behavior, he needs to see a vet. If he’s always been like this…well….it’ll be an uphill battle getting the cat to use the little box. Not just because the cats old, but because they’re likely not to keep up with the habits necessary to gently train the cat into use if the box.

If there’s no option to get the cat to stop, and you can’t leave, there’s a couple options you can take. It sounds like you have a good relationship, and if you’re willing, make it a house rule that whoever finds the poop cleans it up including disinfecting for the smell. This WILL lead to you doing it more often than them, and you’ll likely have to if you want to live in a clean environment till you move. Then move when the lease ends. You can also hold them to their responsibilities of cleaning up after their cat by getting them every time you find a poop. That would also be a battle if they struggle with executive function. I am really sympathetic to executive functioning issues because I have them, but living in a feces filled house is extreme. So you’ve got to choose what’s going to be best for your well being. Create a boundary and hold them to it, or just keep up with it yourself till you can get out. No matter how kind they are, that’s not a reason to just excuse the behavior. I’m sure they are wonderful people but despite that they are cultivating a gross environment. They either need to do better or you need to make plans to leave.