I am vegan for ethical reasons. If one does it carefully, it is not worse than any diet with meat health-wise. So essentially killing animals for food is not necessary and one does it out for pleasure or out of laziness.

As for other points, most fruits are not particularly dense in calories and one needs to eat kilograms of them to consume 100 grams of fructose, which one can get from one bottle of sugary drink. Dates and dry fruits are exceptions, so to minimize fructose exposure one should not eat them in substantial quantities.

As for deficiency, consuming reasonable variety of starchy vegetables and grains with some greens without added oil provides all minerals and vitamins one can get from meat except for B12 as long as one gets enough calories. There are some individuals where a particular component is not absorbed efficiently if it comes from plants, but that is trivial to compensate with supplements. For example, I personally get low on iron (a family run condition) and has to supplement that either directly or indirectly by taking vitamin C with iron-rich vegetables or grains.