That's the point Aliens had to go that route and left the space ship, unfortunately Bioshock 2 was  hamstrung in where they could go since Bioshock is the story of rapture' the ideology that drove it and it's collapse into drug fueled madness, very few games are so tied to a particular setting. most have a central hero who can be moved to where ever you want, any way it was only bought up to show how hard it can be to go back to the same story ,  the real point and I come back to it again is expectation , I feel that if people rather than enjoying another journey through rapture with a great protagonist, simply  expected to be enthralled the same way the second time their expectations were skewed. It was never going to be the second coming of bioshock. 

That's ok' after all we on this site still hope for megaton reveals every E3 even though history tells a different story, my whole point is and it's never been about defending the game or denying a lack of wow but being critical of people using that lack without any real context.

Even if we set aside expectations though, it can't really be denied that due to the familiar setting Bioshock 2 didn't quite have the originality or mystery that 1 and Infinite had. And I say this as someone who thoroughly enjoyed 2 and considers it underrated.

I'm  not sure you've followed my argument setting aside expectation leaves us with nothing because people's expectation is exactly what I've been talking about, about the rest I have agreed about lack of originality' I stated that before just like you, It's setting and storyline  pretty much precluded that my disappointment has always been with the criticism it received not being set against any critical thought as to why that's so.