My husband and his mother.. you know where this is going

My husband is an only child to a single mother. He also doesn’t have much family around at all.. two cousins and an aunt & uncle and that’s about it So basically his whole life he has just grown up around the company of his mum. His mum is completely dependent.. she doesn’t work or drive, she has no friends… doesn’t go out of the house & can’t do anything for herself.. she’s completely useless. I also don’t feel like she’s all quite there mentally either I try really really hard to sympathise with her / their situation as a lot of the caretaking responsibility falls on my husband. I have a mum and dad who are still together and still do so much for me & are completely independent so I just struggle to understand how she is the way she is She expects him to take her shopping, buy all her medication, he cleans her house all the time cause she keeps it like a pig sty and refuses cleaning help She’s also quite selfish and doesn’t even care that we have a little baby and that he needs to be prioritising us, she will just expect him to drop everything and call several times asking where he is and when he’s coming to see her on the weekend. He goes there both Saturday & Sunday so I don’t get much time with him and I have no real interest in going there with him either every weekend I don’t really know what I want out of this post… I knew it would be hard for me from the beginning but I just though my husband would prioritise the family he created a bit more but he always seems so obligated to her and feels so guilty about her all the time when I feel like she’s really really manipulative and useless?