What future episodes establish is
irrelevant because at the time I Borg was written, they hadn't happened yet!
Let us get to the basic question: Was Picard wrong in I Borg? Yes he was. According to the Enterprise crew, the virus was sure to work and Picard (who was assimilated by the Borg) did not even mention the possibility that it may not work. The burden of proof is on you Anwar, not them or I. Until you have canon proof that the virus would have failed, you are just as wrong as Picard was.