I'm pretty sure everyone at WS doesn't expect these cases to be solved in an hour. But it's been months and years since Lauren S, Holly B, Isabel, Lisa, Kyron, Haleigh, Hailey, Dylan, and so many more victims went missing. How much longer are these families going to have to wait for answers? Does LE still have people even assigned to those cases? I'm pretty sure most cases aren't solved years after happening. So, yes, there is going to be criticism of LE when they haven't found a missing child, which means the child is either being tortured every day, or there's a murderer who is facing no punishment.
How many cases are solved a year or more after the victim goes missing or is found dead? Where it takes a year before there's an arrest? Not many. It's not a ~waiting game because with most cases, if they aren't solved within a very short time period...They aren't solved at all. A case's chances of being solved does not increase as time goes on--it decreases.
ETA: Also, LE in Jessica's case did warn the community. You can't just disregard it because it didn't happen in your preferred time period. I believe the warning was right after her body was found. If a child was found dead, and LE say "A predator is on the loose" immediately after, that would be considered an adequate warning, right? I guess they could have warned everyone right after she went missing...but they still warned people, so to me, it counts.