I disagree that fussy eating doesn't impact partners and families "at all really". I have a partner who has a number of food dislikes. I try to cater to him, because I am not an asshole, but it does affect me and our children.
I am the one responsible for meal-planning in our household (god knows I have tried to get OH to participate, but he won't), and do the majority of the cooking. We have small kids, so we need to eat earlyish, before their bedtime. This means I have to cook weeknights, as OH only just arrives home in time for dinner.
I think it's important to eat as a family, so I accommodate OH's tastes. This means there are a lot of foods that I enjoy and that I would like the kids to be able to eat that we can't eat as a family. To be specific, before I met OH, I would eat dinners including foods that he won't eat 3-4 times a week. So it has been a significant compromise for me. The kids also miss out on experiencing these foods, as they're not really foods that it's practical to make for breakfast or lunch.
If, say, I decided to choose to cook those foods a couple of times a week, and let OH fend for himself, in practice that would mean that instead of sitting down to dinner with us, he would be in the kitchen cooking himself something else. When it's time for the kids' bedtime, he'll be eating dinner, so I'll be doing those bedtimes and the kids will barely see him on those days. It breaks down family time, which some people don't care about, but I do. Dinnertime is basically the only time the kids see OH five days a week.
If we go out to dinner (rarely), there's no point going to the increasingly-popular 'tapas-style' restaurants, as the things I will want to eat (ie the foods he won't eat at home, which I rarely get to eat) won't be acceptable for him to share.
As others have mentioned, dinners at family or friends' houses requires a discussion "Will OH eat this? How about that? What will he eat then?" Embarrassingly, he's even refused offers of a serving of something he doesn't like with "No, I find disgusting", when it's a dish that the person has put a lot of time and effort into, and can't see how this is in any way rude ("What? I'm just being honest!").
It's frustrating for me, as there's absolutely no give on his part. Any suggestion that he might even try something different that would expand the range of family meal possibilities is met with scowling and outright refusal even though, as I mentioned upthread, I know he's actually consumed those foods inadvertently at times without any issue.
Compared to some, my OH's tastes are not even "all that bad". I can only imagine how frustrating it must be for people like the OP.