The technology exists but the false positive rate is high, most cameras don't actually implement these things and there is no convincing evidence that all cellphone cameras are secretly always on (though a compromised device could be).
I tend to think of it this way: it's theoretically within our technological capabilities, and has been for at least a decade. However, it's fractally difficult - there are technical challenges, political issues, PR issues, principal-agent problems, all mixing together - and importantly, there is no strong enough economical (or political) incentive to do it. Not when doing a small fraction of work, and a shitty job at this, still showers you with money while avoiding most of the problems.
An not to push my favorite TV show that doesn't involve aliens from outer space too much, but recent advances in AI are changing the equation here, making Person of Interest even more accurate and relevant than it already was.
The more disorder we see, the more people are going to reach for these extremist solutions.
It's all scary - until one is the victim of a crime and the police don't think it's worth following up, or the presiding judge decides your time and suffering is less important than the future prospects of the criminal.
It sounds logical but at least in the case of China there was no disorder to begin with, it's always been relatively safe in terms of violent crime. In China, the violent criminals are the government and the police. You can become a torture victim for as much as splashing ink on a Xi poster or just being Uyghur and existing.
The cameras are not there to protect you from crime, they're there for control, to protect the CCP from the people.
I'm not principally against surveillance for public security but it's very hard to not have it abused - for a start you need authorities and a police force that have good intentions and work for the people, not against them. In most countries that's not a given.