My friend has this deal with crunchy vegetables, and onions in particular. He's always picky and has to custom-order nearly everything he gets. But I came to understand that things taste differently to him. While when we were younger we'd give him shit about it or wonder what's up, we matured and understand that everyone's taste buds are just different.
Flip side, my girlfriend's son has a debilitating eating disorder. He will only touch things like fries, breadsticks, little debbie.. it is debilitating in that he fears humiliation in public from not only being vegetarian, but not being willing to touch a vegetable that isn't a fry.
It is indeed a complicated topic. You can't just make your kid not be a picky eater, but you can help them realize they may adjust to like some things without being a fucking dick. You probably should work to figure out what it is that they just can't stomach. Not restrict meals to be a dick, although once or twice I can see and only out of stubbornness - like as if they will not even taste it and you know they haven't. Sometimes they're stubborn and that's the reason. I say if they taste it a few times (in various dishes) and they still won't do it, they just don't like it and will likely go into adulthood without ever liking that food.
We do have some innate ability to adjust to foods, because it's natural to eat what is edible, in order to sustain ourselves, I suppose. It's possible our massive amount of choice in the first world leads to some of these things. You only have so many calories to expend per day and maintain a healthy weight, why waste them on shit you don't like. There are extremes and norms with regards to pick eating. One is entirely normal, not liking shit like diced tomatoes, onion or mushroom in any dish, another is to be so picky that you yourself admit you have a problem that you cannot fix and need cognitive behavior therapy to not literaly fear food. I think OP's post doesn't take these into account. With my girlfriend's grandson we are sure going to mince up things he might be averse to as a child to get his taste buds acclimated, I suspect a lot of it happens in youth.. but acquired tastes are a thing and if he hates shit despite several tries we will have it when we eat alone and not when he is visiting, so he can have an enjoyable meal too.
Personally I'd go with some positive reinforcement and offer something you know they love as a reward when they just haven't tried something yet. It may work, they may be weirded out by some new vegetable or dish and be totally cool with it after a few bites. If they try, you try, hold your patience. Don't be a dick to your kid and make them go to bed hungry just because they don't like the same things you do.