They kind of are, but not in the way we consider the term. Broad spectrum or non-selective on a label means kills/has effect on everything or many of that type (insects or grasses). Most insecticides, especially residentially labeled products, are selective. Spectracide kills ants, Acelepryn (which we can't get in Maine but should be able to), kills weevils, grubs/the beetles they grow into, and cutworms/sodwebworms. Insecticides and fungicides all have specialties

Most products are also only effective in certain life cycles. If you water down a grub treatment, it's not going to work on surface feeding insects. Depending on what you can get, it also likely isn't going to kill beetles anyway. Products like Provaunt that inhibit the growth of eggs only work on egg laying periods.

Insecticides may have other things written on the table as effective, but that usually a low bar. University of Kentucky has good trials of herbicides and Penn State has been doing some good stuff with White Grub trials.