It is quite certain that law enforcement has more capabilities than they are willing to reveal in courts. Even if encryption backdoors were available, it is dubious they would routinely submit it in evidence.

Encryption is not an impediment to an investigation into an ongoing activity, files need to be decrypted, there are side channels everywhere, etc. Metadata and physical surveillance is enough to convict or put a person in a position where they could be convicted under some other law if there is no convincing explanation for why they were where they were.

Usually the point of mass surveillance is to retroactively look up a person of interest and blackmail them.