I have discovered that a whole-food plant-based diet finesses almost all the problem issues you describe. By cutting out refined and highly processed foods, along with meat, dairy, and eggs, I find it easy to get a balanced diet (in terms of macronutrients) while eating foods rich in micronutrients. I do take a B12 supplement, but that is recommended for older people regardless of their diet. The food is in general not very calorie dense (though there are exceptions, such as avocados), and you never have to read food labels since whole plant-based foods — dried beans/lentils, intact whole grains, vegetables, fruit, nuts/seeds — don't have labels. They are just natural foods.

Update: I should add that adopting a whole-food plant-based diet still requires making good food choices. For example, a decision to live exclusively on fruit (or on uncooked foods) is unwise, to put it mildly. I have found that the Daily Dozen template that Michael Greger MD sets out in his book How Not to Die encourages a good variety — see “Dr. Greger’s Daily Dozen in Practice” for how I adapted the approach. Another idea is to eat foods in a variety of colors (as recommended by David Heber MD PhD in What Color Is Your Diet?) — at the link is a printable checklist to help with that approach.

I continue to eat beans and intact whole grain at each meal, augmented with Greens, Cruciferous Vegetables, Other Vegetables, and Berries, and each morning for breakfast I eat three pieces of fruit (right now a mandarin orange, a persimmon, and a pear).