There's a ton of factors, insulin resistance, glandular stuff, genetics. Goals and Discipline helps lose weight, rather than motivation. Eat enough to be fed, but don't gorge yourself until completely stuffed. Some people eat Fast Food and it ends being the recommended daily caloric intake for that single meal, while they eat 3 meals typically.
I agree with what you say, but most people are too lazy to Count calories, carbs, and macros, et cetera. Best advice, drink more water, cut as many sugars as possible, avoid complex carbs. So, less breads, pasta, and starches.
Eat more leafy greens, see how much protein you need for your weight and body type, focus on Protein and Fibers over Carbs. Live a less sedentary life, so walk around a bit, be a little more active,, it helps circulation in limbs and the cardiovascular system. Have cheat days as a treat, but snacks like chips, cakes, sugary drinks, are a big downfall for people. Plus, once you wean yourself, and then start snacking again you end up over indulging, which is bad.