What we all need is not another fad diet or fasting strategy or super food, but rather a process that looks like a flowchart so an individual can achieve certain goals. I'd be shocked if we ever found a one-size-fits-all diet, but there should be some kind of process to design a good diet specific to an individual, using feedback from measurements like weight, blood sugar, vitamin levels, energy levels and mood.
Want to lose weight? Try fasting for a month. Then stop and try calorie restriction for a month. Was one easier? Did one help you lose more weight? Make adjustments to the more effective one and keep going.
Want to have more energy? Pick a group of healthy foods eat only them for a week. Then, pick a separate group and do that for a week. Journal every day so you can make comparisons about how you feel and how much energy you have.
Wondering what foods are making you feel tired/sick? Pick a handful of vegetables and eat them for a week, then slowly add in the usual suspects that might be sapping your energy. When you find the food that's slowing you down, cut it out of your diet permanently.
Want to save money on groceries? Find the foods that are working best for you and swap out cheaper alternatives or buy in bulk.
I have no idea what the process should look like, these are just possible examples, but a process is what I want.