depends what you’re trying to do. there are plenty of alternatives for spreading on toast or frying/sauteing. but it’s still a pretty central ingredient for western cuisine. I have no idea how I’d make a vegan roux, just for example. my guess is that would break the illusion of whipped margarine pretty quickly.
definitely more restrictive but i think the dairy/cheese thing is the big one
people also feel that vegans are judging them morally and people are very defensive about their eating habit, hence the dislike