I know what you mean, and my answer probably wont be very satisfying to you: Use common sense, eat what your grandma tells you (if you have a good grandma), ignore all the crap on the internet which is 90% confusing rubbish (with the exception of some scientific studies which can be insightful but not necessarily anything to base a diet on).
Try to cook your own food at least half the time and have a balanced intake (just the basics: meat + veg + fruit), if you stick to natural unprocessed foods it's pretty hard to go wrong, avoid sugary treats and highly processed food as much as possible, that's basically all you need to know (sounds pretty obvious because it's common sense).
The fad diets and contradicting advice do not arise out of a failure of your grandmas advice, they arise out of supermarket foods, high sugar, high carbs, ready meals etc. Same with the obesity epidemic, it does not come from lack of will power to not eat like most people think, it comes from the laziness and temptation that we all get from supermarkets.
I try to cook at least half the time and keep an eye on my tendency to be lured by what is becoming way over half of supermarket isles these days (sugar and carb packed processed shit), go to the meat and veg isles out of habit don't even walk down the others unless you want to treat yourself (sugar is a treat not an everyday thing).