I can understand your frustration. For many years my recipe collection was a major hobby and DH was a most appreciative audience. Then, about 10 years ago, he developed multiple and sometimes severe food allergies and sensitivities. I mourned for years.
I have a few thoughts.
You've been given some excellent advice, particularly dividing your cooking between dishes you like or would like to try and those you know he likes.
One thing that's been moderately interesting is to work on a highly skilled rendition of the simple food we eat -- for example, a perfect roast chicken.
You might consider serving sauces on the side. He may have more sensitive taste buds than the average person and a teaspoon of sauce over chicken or whatever might taste good to him whereas most folks would enjoy much more.
With some people, "wasn't bad" is as good a compliment as the cook is likely to get. Sometimes it is useful to take victories where one can.
We frequently eat out for breakfast and lunch, less so for dinner. On these occasions, I indulge my desire for more highly spiced food.
Lastly, my DH and I have been married about the same number of years (forty for us this past December) as you. Occasional deaths of people of DH's and my generation (we are both 67), remind me that we will not have each other forever. We have had a wonderful life together and consider ourselves very lucky.
Good luck to you!