Why do you think section 702 seems unconstitutional? It looks pretty legal to me at least.
Section 702 allows to collect all communications between American citizens and non-citizens, and communications between non-citizens, without any warrant. The issue is: does one need a warrant to search any data about a US citizen in 702 collections? Here, the court says it violates 4A.
which is per-se unconstitutional, violating postal secrecy. they still think they are in war-times since the 30ies, and can store all meta-data and content in full. they are in war actually with all citizens.