Reason for the low convition rate [3]. The cameras were too bad:

https://www.tagesschau.de/inland/koeln-silvester-justiz-101....

Perpetrators could hardly be identified

In Cologne, the charges resulted in preliminary proceedings against 290 suspects and to date in 43 indictments against a total of 52 defendants; in addition, six orders of summary punishment were issued. According to the local court, six of the cases are still pending. But most of the proceedings deal with accusations such as theft, robbery or receiving stolen goods. The allegation of sexual coercion was made in only three proceedings against a total of six accused persons.

The biggest difficulty for the investigators: Many of the suspected perpetrators of sexual assaults from New Year's Eve could only be identified with difficulty afterwards. The investigators evaluated more than 1000 hours of image material, for example from surveillance cameras. However, in most cases it was not possible to identify individual persons.

To cite Benefits Street to say the whole of Europe is like that is like concluding the whole of the US is a shithole by looking at 1 street in Alabama where most of the residents are opioid-addicts , or that it's a Somalia-like warzone after looking at Chicago's south side...