The way I see it, it's processing that you wouldn't or cannot do (in a daily basis) at home, is generally likely to either introduce stuff or break down / transform nutriments unneeded for your body that is likely to have undesirable effects.
My rule when I buy stuff all things that count as raw ingredient is ok, then to quickly imagine is there any reason that adding things
or altering the most basic way to produce it can give economical advantage, all this with a quick ingredient check.
Given that, as examples flour is ok, rice and pasta, even pre-cooked is mostly ok, basic canned food is not a no-go anymore.
My rule when I buy stuff all things that count as raw ingredient is ok, then to quickly imagine is there any reason that adding things or altering the most basic way to produce it can give economical advantage, all this with a quick ingredient check.
Given that, as examples flour is ok, rice and pasta, even pre-cooked is mostly ok, basic canned food is not a no-go anymore.