This is false.
NYC homicide clearance rates for 2021 look to be over 70% for the year, with Q4 2021 at 78%. (worst quarter - 55%, best - 86%).
https://www1.nyc.gov/site/nypd/stats/reports-analysis/cleara...
> In fact, the vast majority of police are assigned to tasks like traffic enforcement
NYPD is not known exactly known for a particularly large amount of traffic enforcement, to the point that I think you'd find most residents wish they did more of it.
I wonder if a large contributor to the higher London clearance rate is related to socioeconomic factors or surveillance laws/systems.
The FBI's UCR Data Explorer used to give you an easy to use breakdown of crimes and clearance rate at the national/state/metro/city level, but unfortunately they redesigned it and now it is both harder to use and presents less data. I guess that is one way to hide data that isn't favorable? There seems to be more emphasis on the danger presented to law enforcement officers, but the #1 cause of death for officers by a large margin, per https://www.odmp.org/search/year?year=2021, has been COVID.
(I'm using "guess at" to refer to clearance rate because if the cops tell a prosecutor they think you murdered someone and the prosecutor says it was obviously someone else so they're not charging you that's generally counted as cleared.)