I agree with most of what you've said. My mother and husband are both doctors. They've seen all body types and have certainly witnessed to myriad of complications that can happen from lack of exercise and unhealthy diet habits for BOTH skinny and obese alike. Your weight isn't the only determining factor to health. And too many people depend on only looks and weight to be the determining factor of health.
I've also watched both of them throughout the years with their own habits. Both are probably two of the healthiest Americans you will ever meet.
My mom eats the same ten, healthy meals on rotation every week (with the four weeks of vacation as "light" exceptions). If she goes out to eat, it's guaranteed she will get the lean fish and steamed veggies option or whatever that equivalent is. When I was growing up, she used to wake up at four thirty to exercise before work, where she would still get at least 10,000 steps a day. (She doesn't need to wake up that early with no kids but still exercises 6 days a week.) On weekends, she still bikes to go paddle boarding in the mornings and then goes to our local cafe spot to eat the "heart healthy" breakfast. Two eggs, whole grain toast and fruit. She almost never deviates from these routines. Never orders fast food (although sometimes my dad does).
My husband is a runner. He runs an hour every other day, but does pull-ups, push-ups, sit-ups etc. everyday, even if for only ten minutes. Every single thing he eats, he knows the nutritional value of with the exception of vacations and the weekly takeout meal. He isn't as strict as my mother, but sticks to lean proteins, whole grains, fruits, vegetables and one or two desserts in the evening. He has never been overweight, but still calorie counts everyday. When on vacation, as a family, we are guaranteed to exercise everyday at least twice a day through hikes, paddle boarding, snorkeling, swimming, biking.
Being healthy does take active mental and physical energy and a constant focus. We all have cheat days but the truly fit, only do that about once a week and never overdo it. I don't think what my husband and my mother do is for everyone. They are "motivated healthy". Whereas, I would describe myself and a lot of healthy Americans as "lazy Americans". But it still takes effort and to a point, "sacrifice" if you will.
However, I disagree about breakfast being important. I'm trying to lose the baby weight as a short female. The only way I've been able to stay at 1200 calories is skipping breakfast. I'm not typically hungry until noon, although I do drink coffee in the morning. And I basically like to eat a 400 calorie lunch, 200 calorie snack and 500-600 calorie sheet with a 100 calorie optional dessert. I like eating larger volumes than 300 calorie meals. That personally makes me incredibly hungry and unable to sustain weightloss. But, I also realize that once I hit maintenance, I will probably add back in a 400 calorie breakfast. My maintenance calories are about 1600-1800 and that is easy to sustain with a breakfast. We each must choose our own path to weightloss and a long-term healthy lifestyle. Breakfast doesn't work for everyone just as keto doesn't work for everyone. Finding your healthy fit is the most important thing.