Low carb and periodic water fasting (autophagy), and you should be set old age.
Baby boomers are deadset on this idea that cardio is the only kind of exercise that one should be doing.
Free weights were considered "dangerous" for a long time. Frankly, most people who lifted back then were suspected of being homosexual.
If you take boomers as being born between 1946 and 1964, then the leading edge of the boomers were turning 30 about the time both Fixx's book and "Pumping Iron" hit the popular conscious. There is a lot more money in selling shoes to people than gym memberships, so saturation advertising is part of the 'why' as well.
Possibly, but we are, after-all, of a different era, when running (Jim Fixx) and aerobics were 'sold' as the right stuff.
(I'm a trailing edge boomer, and I lift.)
"enough sleep, cardio and some resistance exercise"
If you're thinking in terms of "holy grail," you may be subjecting yourself to an "all or nothing" fallacy.
Generally, we're discovering how to lead our bodies through the healthy operating conditions which kept our ancestors alive as we navigate a modern world of high-tech capabilities, treatments and availability crossed with widespread lack of discipline and healthy habits.