England & Wales (because policing is a devolved matter in the UK) have very robust crime recording rules. Consequently, the detection rates are low because you record and close crimes where there is literally no prospect of a conviction.
You compare this to, say, Japan, where an investigation only starts if it’s likely that the crime will be solved, and you have an explanation for why detections seem comparatively poor.
There is also the fact that, despite TVs assertion to the contrary, that solving crime is not easy and it is also true that being able to operate a fully encrypted communication system makes it harder as you rely on mistakes.
As we saw with Encro, criminal groups with Signal and modern iPhones can communicate with gay abandon if they maintain decent opsec.