What does “less adoptable pet” mean? In the world of cats that’s sometimes the black cat. Black cats are often the last cats to be chosen. Cats with litter-box issues are less desirable. I once brought home a lovely adult Persian cat, and the first thing she did was poop on a brocade chair my grandmother had given me. I called animal control where I found her (it used to be known as the pound). They checked this kitty’s file and reported that’s why she was relinquished. She liked using furniture as her litter box. Yes, I returned her. I know people who are set up to handle this type of problem cat. I was not.
Later in my life, I did love another cat with litter box issues for 17 years, though—changing my ways because he was never able to change his. We went from having a fully carpeted home to removing most of it and restoring the original wood floors underneath. And we used a lot of pee-pads. Sure, before this we tried everything recommended for such issues and nothing worked, so we worked (and cleaned) around Max, who did the best he could at being Max.
Other less adoptable pets are those with disabilities and chronic illnesses. If you have the heart and the space to facilitate such a cat or dog or horse, adoption fees are at least lowered for such animals at most shelters this week. So this is the time to consider it.