My fiance doesn't listen and doesn't retain advice

My fiance and I have been together for about 3 years, friends for 10 years. When we first started dating I was living on my own in a large city and him back in our home town with his parents. I was 25 he was 27. Throughout our relationship I decided to move home to continue our relationship and then we became engaged. Until I moved back to our hometown I had lived on my own since I was 20. We lived with his parents until we bought a house a couple of months ago. He lived with his parents until he was 30. Since moving in together we have started fighting more and it typically surrounds his lack of essentially doing things on his own. A few examples are cleaning the bathroom - I had to write out a detailed list; step by step, products to use, etc. on how to clean the bathroom. I have to ask him to clean if I ever need help. We started therapy and our therapist stated he needed to eat better and she even had to tell him to meal prep or maybe cook dinner once a week so I don't always have to do it. When he does cook it feels like I am doing it anyways because he is constantly asking questions about what to pick up from the store, how to cook the food, what to season it with, etc. He also discusses big things with his parents without even consulting me i.e. buying a new car. He didn't even know how to properly fill out a check when we first moved into our house because his mother did it for him in the past. Needless to say his mother always did everything for him and babied him literally until he was 30. When we talk about things in therapy he will change his behaviors for a few days and then revert back to old behaviors. I feel like every time we talk about things, go to therapy, fight about things I am wasting my time because as stated before it will change for a couple of days and then revert right back to the same behaviors. How do I help him stick with things? I have tried to be patient but I am at the end of my rope. I don't know what else to do and I am getting to the point where I just cannot live like this any longer. How do I get him to act like an responsible and fully functioning adult. I know that sounds harsh, but I have been trying to help him and I am exhausted because I am essentially taking the place of his mother and having to do everything for him. Any advice would be appreciated because I do love him and want to get married but I cannot marry someone that I feel like I have to mother. I feel like that would just be setting myself up for failure when it comes to major things happening in our lives such as having kids, dealing with larger issues, etc. because I will have to bear the weight of all of it and have little to no help from my partner.

You're going to have to decide if the relationship is worth it. He has gotten used to people doing things for him, since he lived at home for so long. Some people just don't change, and you need to decide if the rest of the relationship makes it worth it and if this is something you can live with. I've been married for 15 years, and we have a lot of the same issues now that we've had for 10 years. Some things just don't change.

The mind does what it is trained to do. . . . . I want to leave it at that and let you think about what that means. Get a piece of paper and collect your thoughts. Hint: training programs can be changed. If you want me to share more thoughts I have some notes ready. I just want to give you a chance to think about it.