OP we had a drastic and picky menu change due to DH's complex medical diagnosis a couple of years ago. I had the same sinking feeling as you when it first happened but we've adapted and found different ways to enjoy food.
Some of the things we've done that might work for you -
I've been making my own piccalilli and experimenting with tarting up low fat mayonnaise into something more tasty. And on fish - something we'd become quite basic with over the years. Now eating much more of in a lot of different ways. I'm also experimenting with baking in ways that avoid flour, haven't had much success yet, but it's a work in progress!
DH has focused on mocktails and makes a mean ginger mint refresher and on salads, which allow huge variety.
We do miss the foods we used to love, and the wine! But we've been really enjoying all the foods we've discovered since. Fish has been a big revelation. We ate it before but only salmon and tuna and the occasional trout. Had kind of forgotten about it, I guess. Now we try all sorts and are loving it.
Eating out is a lot harder. If we try and be spontaneous there's a reasonable chance DH won't be able to eat a full meal. So we eat at home more. Make the effort to set the table properly, light candles, play music, etc. Enjoy the process. We mainly use recipes off the Internet, but we still have a bunch of glossy recipe books that give us ideas and inspiration.
Nevertheless, we have found a few local restaurants that work well so we savour them. If we're going on a break somewhere we put in the effort to identify places we can eat ahead of time, and we have had a bit of a focus on picnics. We have a nice, well provisioned picnic basket in the back of the car and can put together a great lunch from a supermarket anytime (Have had a few rained out meals stuck in the car which were only fun in the "OhMyGod, do you remember when..." sense. But then we've had the odd awful restaurant meal, so it's probably not any worse overall.)
We go out for coffee and ignore the cake. It was a big deal at first but with time we don't miss it so much most of the time. Looking on the bright side, my metabolism has slowed so much I needed to give up the cake anyway, so it's been kind of useful to have DH as the push on that front. DH has taken the opportunity to become a bit of a coffee snob and recently invested in a fancy espresso machine for home and I'm looking at pour over sets - another food focus that we weren't as into before.