Indeed, it could be argued that it's unrealistic that any of the great technologies our heroes encounter could be put to use within the lifetimes of the heroes. Even if the technologies aren't booby-trapped or otherwise secured against possession by primitives, they should simply be too advanced to be comprehended by the Federation. Sure, Kirk or Janeway can push the buttons of an already existing alien machine, but building one out of scratch should be impossible.
In this respect, things like slipstream drive are problematic because Starfleet or Janeway's crew did not lose the resource required to understand and install this technology - Seven of Nine stayed with them. But Janeway's ship was short on resources in other respects, which may have stopped them from trying to develop slipstream further.