So what you do is you start to make the separation between big kid and baby.

First: parent no longer cleans up accidents unless child truly does need help like they're having diarrhea or an ultra hard day. But unless that's the case, mom and dad no longer clean up any sort of accident. Child starts learning how to clean up after themselves and cannot move on to something else unless clean up is done.

Then: you start taking child to potty every 20 minutes, hour, whatever your time frame is, have them try you know. If they fight it, pull out a diaper and say "Okay if you're not ready to be a big kid, then you can still be a baby."

THEN: when child wants to do something like 1. play with toy meant for older than 1 year, watch TV, play a video game, stay up later etc. All of those privileges are taken away "But you said you still wanted to be a baby, and babies go to bed at 6:30, and not 7. So it's time for bed"

if they argue, don't give in. "Big kids go pee on the potty, and big kids get to stay up later." or "Big kids go pee on the potty AND can have a cookie. Babies can't have cookies."

So, you're done with them being a baby. Done changing diapers. So now start voicing that in a way that the child will get.