True. Mealworms are a poor choice...they are not easy to digest, you need to disable their heads before feeding (they can bite) and they are very incomplete from a nutrition point. You are better off not using them at all, there are plenty of much more suitable invertebrates.
If the animal is in a forest-type tank with leaf-litter and stuff, having a few earthworms around will be benefitial, as well as woodlice, springtails and even small slugs.