Considering the rise of the far right in the last EU elections, anyone who's seriously considering weakening public encryption must be out of their minds.
The "solution" would have been abused for other surveillance or been used as a rationale for even more surveillance.
It is a social issue that does not have technical solutions. The worst abuse cases (like the horrific Regensburg Dome boys choir case: https://www.theguardian.com/world/2017/jul/18/boys-abused-ge...) occurred before the Internet. If the EU is so interested in the issue, how about prosecuting known cases instead of a half apology. Chat Control could have done exactly nothing here.
I think the number of false positives would be in the millions after a few weeks if not a few days.
That is why such a system is simply not workable.
There will always be tradeoffs between security/privacy and enforcement. There are ways to target harmful content without undermining E2E. There is no way to replace the privacy and security guarantees of E2E.
You might wanna consider that the people you critique here already weighed the pros and cons of the question. E.g. I am pretty convinced some crimes are also discussed in European bedrooms while people have sex. Yet for some reason I believe the police should not be allowed to spy and listen to things happening in every bedroom indiscriminately.
In a world of AI you either have private communications or you don't. In the analog world of the past surveillance systems were still limited by the number of people you had to employ to listen in on your population. This is no longer the case. And that no longer being the case shifts the power dynamic between the state and its citizens in favour of the state. This can be a real problem if you you trust your state, but becomes a terrible problem once you have people in power who don't believe the people are entitled to choosing their leaders.
I don't buy that police is suddenly unable to figure out crimes just because they are unable to read every conversation people have on messengers. If you want total safety and you're so frigthened of the world that you long for a all powerful leader that has insight into all our lives, I got bad news. Historically that kind of arrangment hasn't been particularily safe or stable, because such a leader doesn't care about people doing a good job, he cares about having loyal people around him. And that means all the lower ranking people will be left to fight among themselves, as police is no longer doing the job of keeping people safe, but the job of keeping governments safe.
Our democratic systems are brittle and every power you give to the state or other actors needs to be considered in its consequences.