Well, I don't know exactly what an "Arbiter Pro Jazz" is, but I bet it's a Far Eastern copy of a Selmer Super Action 80. So, tonally, it's probably going to be in that Selmer ballpark - the Super Action 80 was Selmer's own copy of the Mark 6, with refinements. I mean, it won't be exactly like playing a SA80, either mechanically or acoustically, but it will probably be a lot closer than if you had a Conn or Buescher.
Now the thing might be suffering mechanically, and that'll be a drag. But you said "almost unplayed" - I'd bet that you've got a couple of pads that need to be reset, or a loose pivot screw, or some of that kind of thing. It's also possible that it was built with such poor QC that no one can get it reliably in adjustment. But I rather doubt it.
I wouldn't jump out there and tell you not to buy a new (or new-to-you) horn if you want to, but be advised that if your goal is to practice and develop some Getz stuff, buying a horn may well not be the direct path to it.