It seems like given the enormous amounts of blood, sweat and treasure that have been expended in the investigation of long and short-term effects of particular diets, probably the most consistent result is that the null hypothesis prevails for almost all dietary interventions that don't modify caloric intake.

This is most dramatically illustrated by the Women's Health Initiative study, a very large-scale RCT of low-fat diets. A couple of representative results are at https://pubmed.ncbi.nlm.nih.gov/16467234/ and https://pubmed.ncbi.nlm.nih.gov/16467232/ and https://pubmed.ncbi.nlm.nih.gov/16391215/; they did not, in general, find any meaningful differences between the low-fat and control groups in terms of cardiovascular disease risk or breast cancer risk, which were their primary endpoints. (The small and mostly non-statistically-significant results they did observe are difficult to untangle from the average 2 kg of weight lost by the experimental group.)

All told, it seems like the only two clearly-demonstrated-important aspects of nutrition are:

1. You get calories at a rate that puts you in the healthy BMI range; and
2. You don't suffer any specific nutrient deficiencies.

Everything else is clouded in layers of controversy fueled by observational studies with varyingly-dodgy attempts at controlling for confounders.

As such I tend to view pretty much anything I'm eating in a given day as normal and healthy based on whether it allows me to stay within my desired caloric intake. Most of the time it's quasadillas with low-carb tortillas, Catalina Crunch cereal, eggs, milk, and frequently McDonald's breakfasts (I'm actually very fond of their biscuits.) And carrots. Lots of carrots.

My approach is to simply set a daily nutrition target and try to follow it as closely as possible. I use a tracker app (currently Cronometer, there are a few alternatives) to keep records and plan meals.

I track nutrition targets for both macro-nutrients (proteins, carbohydrates, and fats, where my choice is P25%-C5%-F70%) and micronutrients (vitamins, minerals, omega3, and essential amino acids - according to published RDAs / specific medical advice). 

Of course, daily caloric input (carbs + fats) is adjusted for body composition and physical activity.

I will start with more details about our soup parties (or how they were before Covid19): It is a bit of put-luck: It is common to bring some snacks, fruits, or sweets. But the main dish is almost always a vegetable soup, which we prepare together. There are frequently vegetarians, so we mostly have two pots, one with meatballs and one without. Rice and noodles are usually provided, and some of the kids prefer the noodles without anything else - maybe just some of the liquid of the soup without the vegetables. And that is OK. Vegetable soup is an exaggeration. A big part is potato and with all the rice and noodles it is a lot of carbohydrates. And that is OK. After the soup, the sweets and snacks are opened (the kids mostly try to get them before the soup). Sweets and snacks means chocolate, gummi bears, chips, and stuff like that. For a party that is OK. And parties like this happen every other week. We drink fruit juices, water, and tea, rarely coffee. It is very rare to drink beer or wine, but I would consider one beer (0.33l) per adult OK.

One thing that I think is OK for my personal diet is my relatively high sugar intake. Over three months, I measured my sugar intake from sweets (sugar from all other food, e.g., bread, cereals not included), and it averages to about 100g per day. I wouldn't recommend this to others, but my metabolism seems to deal with it fine (no overweight), and the same holds for most of my relatives. I have experimented a bit with my sugar craving, and I can reduce it with some tricks, but as that doesn't seem to have much of an impact, I'm OK with it. I do try to buy sweets and chocolates with less than 40% sugar.