My child speaks clearly outside but their pronunciation falls apart at home. Is it okay to leave it alone?

No need to worry. Being able to pronounce clearly outside, with the listener in mind, is proof they have the ability to speak clearly. Pronunciation falling apart at home is because, with family who understand them better than anyone and the feeling of "I want to talk lots," their attention to pronunciation drops. It's actually a healthy sign. Things you can do at home: 1) Listen to them slowly as an adult. 2) Instead of backchanneling with "uh-huh" or "I see," summarize your child's speech and reply slowly, like "so OO-chan did OO, huh." 3) Converse while writing. These lower the load of speaking so resources can go to pronunciation. It's far more effective than pointing out "say it properly."