Part of the problem with nutrition is it's hard to get quality data, like how do you get long-term studies where you can control every aspect of each participant's diet and lifestyle? The best data we have is all over relatively short periods.
Saturated fat is one thing there is strong consensus on.
https://www.heart.org/en/healthy-living/healthy-eating/eat-s...
https://care.diabetesjournals.org/content/41/8/1732
I'll point out that regarding "healthy" fats, what you see in most recommendations is that replacing unhealthy fats with healthy fats improves heart health, not that adding healthy fats improves heart health.
Eating less meat helps, too.
https://academic.oup.com/ajcn/article/110/1/24/5494812
(surprisingly, in this particular study, white meat was about as bad as red meat)