You can get the nutrients you need on a Keto diet. Again, you can eat fruits and vegetables on Keto.
I eat a lot of avocados (yes, it’s a fruit), and strawberries (which are low-glycemic), and I eat plenty of power greens, brussels sprouts, cauliflower, and broccoli.
There is no essential carbohydrate, there are essential proteins and fats. You can get all the nutrients you need without having eat more than 20 grams of carbs a day.
I have heard similar arguments from vegetarians for most of my life. 20 grams is barely more than half an ounce, if you restrict your diet in this way, you are likely to be missing nutrients that your body should be getting.
But much more importantly but completely missing in most of the arguments from people who want to cut entire categories of foods from their diet is the effect that it has on your gut biome. Healthy people have a wide variety of healthy bacteria in their intestines that not only aid in digestion but are important for healthy living in ways that even now are not fully understood. When you basically cut out an entire food group from your diet entire categories of bacteria that are healthy for you just die out with consequences that are not currently predictable.
You can believe that you know everything about nutrition, and you can find a bunch books with authors who have the same philosophy to confirm your opinion. But we do not understand everything about nutrition and it is risky to alter your diet in ways that are based on someone or some groups’ crackpot theory.
I admit that it is also risky for people to live on nothing but processed foods and all the crap that is pushed on us by the food industry that is designed more for maximum profit than healthy eating. So in as much as you are getting back to the basics you probably are not doing any more damage to yourself than most people are with their choices of almost completely prepackaged foods.