the tediousness of label reading
Shopping takes me longer having to read all the tiny tiny print (sometimes obscured by price labels or wrinkled packaging) and the worst ingredient for me is the ubiquitous canola oil. I really hate canola oil and get so annoyed when it accidentally comes home with me because I was lax in reading every single tiny word. I recently picked up a couple of jams in a country store (their own product) and when I got home I saw the jams had
HFCS as an ingredient. Why would you need to put that in jam!
And then there are the listed ingredients that are so alien they must be looked up online, some are ok and others are nasty.
As Hotoy noted the simple answer is to not buy packed/processed foods. If you make the problematic foods yourself you'll get exactly what you want.
I long time ago i adopted the five ingredients or less rule for the vast majority of food.
The more ingredients the more processed and further away from "food" the end result is. (So called diet foods are some of the worst offenders)