...given my own experience with that Suntour Blue Line derailleur, if it is undamaged and unbent, I would rank it far better in performance than the Campagnolo unit in your photo.
There are a couple of things in your photo that are confusing. I presume you know the cable needs to be connected, but you also have a kink in the cable housing right next to the derailleur that needs to be corrected. That housing is pretty old, and a new section with a plastic liner would probably improve your outcome.

That Blue Line thing is roughly equivalent to Suntour's top end Cyclone of the earlier era. There are no contemporaneous rear derailleurs I'm aware of that do a better job, unless maybe you want to go with something newer.