Potato is not just starch. In fact per calory potato is very dense nutritional wise with all that fiber, minerals and vitamins. In addition there is speed of absorption which for starches is much lower than for simple sugar. Plus starch metabolizes as glucose while table sugar and friends contains 50% fructose.
Which points to an elephant in the room that people miss when use the term carbs. It is the similarity between whole-food plant-based and various forms of keto.
They both avoids simple sugars and processed flour mixed with refined seed oils or saturated fats.
Bananas and dates (to name a few fruits) are plants, are whole foods, and are filled with fructose.
A single potato with skin has 6 grams of fiber and around 60 grams of starch.
As for the vitamins and minerals, the only thing found in a relevant amount in potatoes is potassium. Contrast this with eggs, organ meat or even muscle meat.
What would you say is the problem with saturated fat?
As for saturated fat I have no idea what if any can be wrong with it from human health point of view. Literature and observational studies are contradictory and it all depends on the whole diet. But I do know from personal experience and from some hints from literature that mixing it or vegetable oil for that matter with highly processed starches or sugars is bad.
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.
Which points to an elephant in the room that people miss when use the term carbs. It is the similarity between whole-food plant-based and various forms of keto. They both avoids simple sugars and processed flour mixed with refined seed oils or saturated fats.