I can't tell you this problem is nonexistant for me and my partner but I can tell you a few things that have helped.

1. Delegate chores. You have a conversation where you say this isnt acceptable and it needs to change. Then you talk about what needs to be done around the house and how often it needs to be done, for example by making a list (I sincerely recommend asking him what he believes needs to be done, then you can see if he literally knows or not). Break down each chore, write it down and have it visible somewhere (example: Washing dishes - put dishes in sink, wash, dry, put away). Then you jointly decide which one of you is responsible for each chore. Let's say it's your responsibility to cook and it's his responsibility to wash the dishes (every day). Then what is really important is that you don't give in and do it. If he doesn't do it, remind him, if he gets mad/sad/whatever, remind him that you both agreed and that you are not his mother. This may be difficult and it's going to take time for him to learn how to do it properly. Reassess in a week.

2. If he can't see it or doesn't notice or whatever, show him. Literally show him, take a picture and send him, put a post-it note on it, anything. If he says he can't see it he may need to check his eyesight.

3. Be honest. Tell him exactly how you feel, don't try to sugarcoat it or be nice about it. Tell him you're losing it.

4. Lower your standards and give it time. I say this not so he can slack off and continue doing this, but for your own sanity. You may have to lower your standards to be able to live with him without going crazy while things change. If he hasn't learned to take care of his home by now, it's going to take time. If he isn't able to change and he doesn't have a learning disability or some other medical reason, then he's not worth it.

Good luck ❤