Somehow the police managed to catch bad guys before mass surveillance existed. Maybe they should look at that?
This line of thinking has always struck me as extremely odd - as soon as current, presumably E2EE, methods of communication are tapped into for intelligence and law enforcement purposes, criminals can and will switch to projects that don't comply with the backdoor laws. It's a violation of privacy that only law-abiding citizens will be subject to, for everyone else it's optional.
You might catch a wave of them off guard in the beginning, but in the long term all you end up doing is surveilling innocent people and maybe catching lowest hanging fruit - the types of people who are already dumb enough to share their criminal activities on Facebook.