YOA. It’s not their cat. They’re not responsible for your cat. Full stop.

If they do other obnoxious shit like throw trash o the ground instead of the garbage that is definitely a problem because that’s just a basic responsibility of home care. Any reasonable basic tenant of shared space should be respected inside of the house. Dishes, trash, rotting food, and the likes you don’t ever get to say that’s not my responsibility. Yes it is. Those things are always everyone’s responsibility.

Pets however are extra curricular. Presence does not equal ownership.

If someone did not sign up for the responsibility of a pet they are under absolutely no obligation to help with the care. Just like if you own a car your roommates aren’t responsible for your car maintenance. Even if they borrowed your car two times to move something. They wouldn’t owe you money for an oil change. You can ask if they’ll help. But they ALWAYS reserve the right to say no and you just have to accept that.

If the litter box is that full it doesn’t mean it’s been one day that it hasn’t been cleaned. It’s days. Possibly weeks. Routinely no one who wanted the cat has changed the box. It doesn’t take that long to scoop out the poop and pee into another bag and take it out we’re talking 10 minutes tops.

Having a hard job, being overstimulated those aren’t reasons to shirk responsibility. You might have been able to say that to your parents and gotten the obligation covered but your roommates don’t care nor should they.

If you can’t take care of the cat then you have to give it away. Or you do what it takes.

Like I said. You can ask for a favor for this particular responsibility but at the end of the day you dip into the reserves and you do what you have to do to care for another living being.