Throw in some nice cherry-picking results, human psychology where the diet didn’t fail you, you failed the diet so people aren’t willing to speak up when it doesn’t work for them, and in todays day and age paid commenters that will bombard YT videos with fake comments both pro on your videos and anti on videos by actual scientists who have studied this stuff and have seen remarkably similar results for decades.
After all, there’s not much money to be made in “eat foods. Mostly plants. Not too much”. Especially when on the other side it’s not just processed foods but even the meat and dairy industries that are massive operations making a lot of money (with some hefty tax breaks and subsidies thrown in to boot).
The answer to “what diet” is “keep trying them until you find one that works, then stick with it.” There is an infinite number of totally functional combinations.
If something isn't working, then sure, look to the science for potential solutions and try them out. Nothing, however is guaranteed.
If you're not getting the results you're hoping for, move on. Conversely, if it ain't broke, don't fix it, even if someone out there is telling you that you're doing it wrong.
For example I have a weakness for sugar cereal. I know it's on the bad list of sweet, ultraprocessed foods. I also know that, as a pre-workout meal, I perform great after crushing a half-box of Trix or Captain Crunch.
I don't think people want that particular diet to work. Granted, it's got its downsides. And you can do it in a very unhealthy way. But being 40 pounds overweight was probably worse than intermittent lower-carb with healthy(er) options like chicken caesar salads, stuffed peppers made with turkey, or tuna salad on celery. It just let me eat less calories without as much hunger.