I agree that one of the big concerns is the source. Most bulk dried mealworms come from China and you don't know what they're being fed or what else might be used in processing. Can be difficult to find US/UK grown mealworms.
I've mostly switch to dried black soldier fly larvae that are grown...
Nothing wrong with them IMO, just don't feed excessive amounts of them.
Black Soldier fly larvae are another option that's similar, though I find them more gross to handle since they're larger.