A lot of people eat vegan food all the time without even realizing it - it's not about eating special health food or just greens, per se, it's just about the absence of all meat, dairy, and eggs.
Vegan food, like all food, can be absolutely delicious or absolutely wretch-inducing depending on quality, freshness, the way in which it is prepared, the way in which it is presented, and the balance in which it is eaten (e.g. just carbs all the time is going to make one sick- balanced meals are a must).
In short, we've all had vegan food before and loved it; we may have not realized it. It's not fair to anchor one's experience with a dried out vegan "cookie" with all vegan food. That's just marketing.