I've been working for the same people as a babysitter for a while now. I watch all the kids butthe main kid I take care of is called James(fake name for privacy) when I first started babysitting, James was a baby so I obviously had no problem putting him for naps, changing diapers and everything else you do for baby's/toddlers. The issue is that James is older now, he will be going to school this year but he is still not potty trained, I've gently brought it up over the year to his mom but she just laughs it off or says she will get on it and doesn't. Every time he goes in his diaper it's a blowout and absolutely disgusting, about a month ago I hit a breaking point when the mom stopped atleast providing gloves for me to wear when dealing with this. He normally goes about 20 minutes before I leave,so after she stopped buying gloves I just started leaving it for his mom to deal with, she didn't say anything until today when I came in and got a text from her basically telling me I need to change him as soon as he goes and that he got a diaper rash. I feel really bad that that happend to him but I can't keep changing diapers of a kid who should have been using a toilet 2 years ago. So AITA for not changing his diaper anymore

CONTEXT: James has no special needs or anything, he's been checked and is completely fine in that sense, his mom just doesn't want to potty train, she's really passive and allows the kids to do whatever they want, and even when I tell her about James general misbehavior she doesn't do anything. So I know it's just her parenting style and not anything serious.