Years ago gun and knife crime was almost unheard of in the UK, even when hand guns were still legal...
Now it's multiple times a day in London.
As
@Burnsy2023 says; attributing a rise in crime rates to ‘becoming soft touch’ is simplistic at best.
It may be a factor, but even if there was evidence to support the hypothesis (I don’t know) it would have to mitigate for a whole host of other factors before ‘soft touch’ could be pinpointed as ‘the cause’.
For instance, crime rates fell ~20 years after the introduction of the birth control pill in the 1960s. The theory is that there were fewer unwanted children who had abusive childhoods and therefore fewer adults who turned to a life of crime.
~20 years ago, the UK had one of the highest rates of teen pregnancy in Europe. Now we’re seeing a rise in crime, especially knife crime involving ‘youths’. This could be just as much of a coincidence as the ‘soft touch’ approach, but it could equally be significant.
Then there’s the correlation between the decline in violent crime and the phasing out of leaded petrol. Obviously leaded petrol can’t be the cause of the spike in crime today, but the point is that there may be environmental factors outside of direct ‘crime and punishment’ policy that could have an effect.