This is mainly a response to the United Kingdom's proposal to ban end-to-end encrypted platforms. According to Article 12 of the United Nations Declaration of Human Rights, "No one shall be subjected to arbitrary interference with his privacy." This proposed bill may violate this human right.
If the United Kingdom created a backdoor in encryption, it would no longer be encryption. The reason platforms advertise encryption is not to include a backdoor that allows everyone and their mother the government to see everything that happens. It is because there are some things that you want to send to someone without making public on the whole internet, like private photos or even passwords shared between family members.
All of the people they would want to catch would switch to different platforms that would keep using encryption. They are criminals, after all, and if they are willing to take a major charge like pedophilia, I doubt switching platforms will make them stop.
The one group of people who would not have to comply is the government, because they don't want all of their encryption to have back doors. If the government is not willing to have its own encryption opened, why should the people? It's just a classic case of a double standard and going down the route of being a totalitarian government wanting to see and control everything everyone does.
If this encryption had a backdoor, everything that everyone wanted to keep private would eventually become public because once hackers figured out how the backdoor worked, it would take days, if not weeks, for the backdoors to be switched or fixed in platforms. These backdoors would be a big invasion of privacy, as all internet activity by normal citizens would be public to the government and hackers. The situation now is that people are holding tons of encrypted information, just waiting for quantum computers to take over and break all encryption. This would make this effect even bigger because you know that within a few years or months everything will be public, and after quantum computers, this will still exist, so there will continue to be a risk.