It's designed for short haul trips.
The definition of those would have to include surviving for two years in Kazon territory, without known opportunities for replenishing fuel or repairing propulsion systems...
Doesn't mean Starfleet couldn't define "short haul" that way, and "long haul" as something like fifty years between refuelings.
I think it isn't so much about what Voyager actually did
, as it was about what it was intended
to do. I don't think a 70+ year journey (or, indeed, necessarily even a two year journey) was the "bread and butter" mission of the Intrepid class. I've always figured that was a unique situation that Voyager found herself in and the crew simply had to adapt to.
I agree with the comparisons to the Constitution class though. I think it's very much 24th century Starfleet's equivilent to the Constitution, except the definition of the types of mission that kind of ship makes have changed since the days of TOS (it isn't IMO a "front line" ship like, say, the Excelsiors, Galaxys or even Nebula classes are).