The issue is end to end encryption.

The law change requires messaging applications to be able to provide messages between people using their service.

In the 00's, messaging applications would have a secure connection between themselves and person A and anouther secure connection between themselves and Person B.

Person A would encrypt the message, send it to the service, who would decrypt it, open a connection to Person B, encrypt the message and send to Person B.

So if the police got a warrent for communications of Person B (say the police think the person is involved in human trafficking), then the messaging service could provide all messages sent to Person B.

Message services have taken themselves out of the loop, Person A now encrypts the message and sends directly to Person B. So the police appear with a warrent and the message service shrugs its shoulders since it hasno means to get the data.

The law effectively requires messaging services to design the apps/service so they can comply with a warrent.

The issue is less encryption and more the balance between your right to privacy and states right to intrude.

This is why banks aren't upset, they aren't talking about back dooring encryption and bank encryption is between you and the bank so they don't have to do/say anything.