Because we already knew what ships from the 24th century were capable of, particularly the Galaxy class (which was brand new as of TNG S1), so a much smaller Intrepid class ship should have had nowhere near the capabilities of the larger Galaxy class ship, especially without frequent stops at a starbase. It would have been more believable in the 25th Century, where random technobabble could be pulled out of their asses and the writer's could pass it of as "oh yeah, that got invented sometime in the last 50 years, you just never heard about it".
So what you're trying to say is that you wanted a better explanation as to why Voyager seemed to be perfectly fine for seven years in the DQ, without starbases? Well for starters, the size of the ship has nothing to do with anything. There's never been any indication that a larger ship is somehow better than a smaller one. TPTB could have made Voyager twice the size of the Enterprise-D instead of half the size, and the stories would have been exactly the same.
And technobabble was already used at an incredible rate in VOY. Why would 25th century technobabble make any difference? Bullshit is bullshit, no matter what time period it's used in.