Help with Litter avoidance

Hi! I have 2 cats. One is 2 years and one is 5 years. I also have 2 young ferrets (who use the litter box too). The 5yr old cat, I took from some friends who could not care for her any longer. Over half the time she does her business, she doesn't use the litter box.

I originally thought it was a territorial thing. But I noticed that she tends to use it more often right after it's been cleaned out. Now, I can see the simple answer is to scoop everyday, but I am quite a busy person and tend to forget to scoop EVERY day (usually every other).

Is there any advice that anyone can give, or am I going to need to make a more forceful effort to scoop the box everyday?

Scoop the boxes every day.

Check for a UTI.

Add more boxes.

Change the litter more often.

I think the key is to scooping more often, because once a litterbox problem starts, they're hard to get back to using the box regularly. And if one kitty thinks the box is gross, then it's possible others will follow suit.