The big guns are already doing it.
It won't help, because the Home Office is run by paranoid authoritarians and crazies, and they keep trying to pull crap like this no matter who is in power.
The critical question is just how likely is it that the gov will prosecute Apple, Google, or FB for not following the rules.
"Not very", I'd guess.
How likely is the gov to prosecute Tiny Corp Ltd?
"8.1 Small companies (with under 10,000 users) will not be obligated to provide a permanent interception capability, although they may be obligated to give effect to a warrant."
But look at this:
"8.17 A person to whom a technical capability notice is given is under a duty to comply with the notice. In respect of a technical capability notice to give effect to equipment interference or bulk acquisition warrants, the duty to comply with a technical capability notice is enforceable against a person in the UK by civil proceedings by the Secretary of State.
The duty to comply with a technical capability notice to give effect to interception warrants and CD authorisations is enforceable against a person in the UK and a person outside the UK by civil proceedings by the Secretary of State."
That's civil proceedings, not criminal proceedings. So basically the SoS can sue, but not jail anyone.
It's all quite confused, and fundamentally fails to understand the differences between targeted surveillance, bulk surveillance, end-to-end encryption, commercial encryption for (e.g.) secure banking, open source VPNs, and so on.
If you pull apart the language, the mental model is of someone who thinks encryption is like an envelope around a letter. So if you demand a de-enveloping tool from the people who make and sell envelopes you've done your job.
There's a bit more to it, but the legal language doesn't have any insight into that.