It seems to me that the answer with the quantum slip screen is outline a "control" problem - so they've worked out how to use it to go 60,000 light years but not 2000 light years, they cannot control the energy to that fine of a degree. That way, the delta Quadrant can be used again but you don't have situation where the Enterprise can be at Earth at the start of an adventure and then at the Klingon home world an instant later.
That's not consistent with the depiction of quantum slipstream drive onscreen; as shown, it requires very precise calculation to keep the vortex stable, so the longer the journey, the more difficult it is.
Besides, we already have stories where the Enterprise
plays hopscotch across the quadrant -- see Doors into Chaos
, for instance. Or First Contact
, where the E-E seemingly got from the Romulan border to Earth within a few minutes. It's been a long, long time since anyone's really bothered to obey the injunction of the original TOS and TNG writers' bibles: "Don't treat deep space like a local neighborhood." The UFP and its neighbors are already hours or days apart, at least when the story demands it. At least QSD would be a better rationalization for what's already effectively the case.