Big bang theory. Hell, probably most of cosmology. It's all a bunch of bullshit. Our main theory was the brain fart of a Catholic priest and that's now considered the "secular theory." You can't make this stuff up.... Oh wait you can. From cosmic inflation to dark matter and dark energy it's all bullshit I'm pretty sure.
Saturated fats bad. Dietary cholesterol bad. Eggs bad. Dairy bad. Red meat bad. And on and on ad nauseam. Nutritional science is all fucking bullshit pretty much, especially when people love to reduce (too absurdity) it to like is that one thing you got to do or the one thing you can't do. People worried about salt when most animals will do things that could easily kill them just to get a little lick of salt.
Importance of breakfast? Whatever. Any meal you eat is breaking your fast. There's no benefit to eating immediately after waking up.
How about the eight glasses of water a day that's a bunch of bullshit.
And considering how much science is epidemiological and it's just associations and no proof of causation but most people will lean on the causation anyway even if it's reverse causation, right.
How about the serotonin deficiency cause of depression?
Does moderate alcohol consumption have any benefits whatsoever?
Are psychiatric diagnosis useful?
Just how important is the microbiome?
Using animal models in place of human models.
How about the replication crisis? How about that about half of all scientific articles are bullshit and many of them get it retracted?
How about the many interpretations of quantum mechanics? Which ones right which are wrong?