Do you have a list of base foods that you're working from?
I have one Autistic child, one NT and one younger child with a current diagnosis of social communication disorder (we think ASD) she has sensory issues with her food texture and smells.
At one stage I felt like I was cooking 4 meals at night. Really soul destroying.
I sort of hit a point where I thought this just can't go on. I was eating less real food and more junk snacks as I was fed up with cooking. I love cooking but not repetative beige cooking - that's just like cleaning the toilet - a necessity but not something I could ever find a pleasure.
I started batch cooking and freezing the few foods we could eat as a family. A homemade pasta sauce that's slightly bland but I serve the children's one with pasta, one with meatballs, one with meatballs and cheese., Then I add a dash of cayene and pinch if chilli to DH's and mine before serving. It's one meal, with a lot less fuss.
Another one we have is rice, chicken and peas. DD has a small amount of rice in one pile, a dish of peas and some sliced skinless chicken. The rest of us have our rice mixed with peas, DS2 and DS1 now have there precooked chicken in a mild homemade smooth curry sauce but initially i did the sauce in a small dish to the side and they used it like ketchup. Then they've moved onto pouring it over. I cant cook the sauce when the DC are at home as they find the spice smell too much but dont when its a small amount reheated.
We've built up a list of staples that I can batch cook, so less cooking, which means I enjoy actual cooking occasionally a bit more.
My elder two are 15 and 12 so a little more open to trying new things. I find if I take all the pressure off and new foods aren't a meal, They're an extra at a different time, most times they will give them a go.
I just wanted to offer sympathy because I think I get the should destroying loss of interest thing.