It all sounds so wonderful to tell others how beautifully open-minded you are, and it's so easy if you've never done it. It's like asking people how they feel about abortion when they have never had an unwanted pregnancy. Let a death penalty opponent have his wife kidnapped, tortured, raped, and murdered, and then you'll find out how he REALLY feels about the death penalty. Same thing with dating someone with significant dietary limitations.
I am currently dating a woman who is not vegan but she is a very picky eater: no red meat, no fried foods, no creamy-textured foods (no gravy, no pudding, no creamed vegetable, etc.), no artificial sweeteners, no turkey, only occasional chicken, some pork. Multi-grain bread but no white bread. She likes chocolate but it must be dark chocolate and not too sweet.
I don't care what she eats. She expresses some concern about my diet and I listen to her and do respond to some suggestions. However. . .
If we want to go out to dinner, the choice in restaurants is very limited. If it is just the two of us, we can always find something where we are both happy (though this sometimes require that I compromise on my definition of happiness.) If we want to meet my parents for dinner, things start to get complicated. If someone invites us to their home for dinner, I must go into the litany of things that she doesn't eat and it is embarrassing to describe someone who eats like a fussy, spoiled child. This is a never ending problem and it is more than a trifling annoyance.
If I had a choice of dating someone with such dietary restrictions or someone who eats a normal diet, I would always choose the one who eats a normal diet. Why add an unnecessary complication into a dating relationship?
However, I am head-over-heels in love with her and I will gladly endure these problems to have her in my life.