But if they couldn't make new allies and figure out how to repair the ship in strange circumstances, they'd look like idiots compared to TOS and TNG. Yes, I can see some patchwork stuff done maybe on the inside but the whole ship becoming some ugly mish-mash is too far and would make them too incompetent.
They'd look like people having a harder time surviving and keeping the ship running, compared to TOS and TNG. Which is kind of meant to be the point of the show.
If you're focussing too much on how good the engineers look you're missing the point. The more important question is, what potential did Voyager have for new storytelling, and doing something different to preceeding shows?