I'm not suggesting you're wrong, but I don't think this is _just_ the UK being a US puppet, there is very much an appetite for it in the UK parliament too.
https://en.wikipedia.org/wiki/Five_Eyes (look also for Nine and Fourteen Eyes on this page)
The cops think this is great, more power in their hands.
The feds think it'll help them out, but those local cops will try to abuse it for sure, let's hope the courts keep on top of the warrants.
The spies already have access that's almost as good by illegal means, without the need for any of those pesky warrants. But it'll be useful not to have to keep their access secret.
The judges think this is a Fourth Amendment bust-up waiting to happen, why would you even... ugh.
The defensive cyber-security types think this is very obviously a bad move.
The diplomats think the Brits are OK and will do their warrant stuff properly, but for sure there will immediately be a request from some oil-rich middle eastern dictatorship for the same access. That will make for some awkward conversations.
The elected politicians in power want to get votes, and are safe against this power being used against them. Being tough on crime and Backing The Blue might be a vote-winner. 95% of voters don't know the difference between "encrypted end-to-end" and "encrypted in transit and at rest" so getting this right might not win you many votes. On the other hand, if this takes off in the public consciousness as snooping, or intrusion, or an expansion of state power, could lose you a lot of votes. Maybe wait and see how the public reacts?
The elected politicians who aren't in power think ooooh boy, this is not a power I want used against me, and not an administration I'd trust not to use it against me.