Let's see weren't both the Lexx and Moya living ships, so they might have some sort of natural repair mechanism. Just as if I cut myself the wound will heal?
As for the Destiny in SG:U it was barely operational as it was, and didn't we have episodes dealing with resorces they need just to stay alive?
Comparing Voyager with three television series that didn't appear until after it was already launched is like criticizing King Henry VIII for not driving an automobile.
Not when they have similar enough premises and committed those same "flaws" Voyager is always singled out for abuse over.
Of course, this is just the tip of the iceberg when it comes to how other shows got away with the stuff VOY was condemned for.