AAM recently had a post from someone who was frustrated with a manager who would only give vague (but extremely negative) feedback about her writing.
Non-specific review comments annoy me as well. They're completely unproductive. For internal review (is what this document up to snuff before it goes out the door), general comments waste the writer's time as they practice mind-reading, and for external review especially if you have a contentious relationships, they give your opponent an opening to bash away at your own credibility.
If you're going to go to the trouble to make a comment, you might as well be specific about what the problem is, even if it's "this sentence is so complicated I forgot what the subject was three lines ago".
There are very few truly "general" criticisms. Boring? Minimize the passive voice, cut down (or at least vary) your sentence and paragraph length, expand your vocabulary. Wrong writing level for the audience? Minimize jargon and use simpler/less fancy words to say the same thing (help/aid, use/utilize, find/locate). Awkward phrasing? Jump in and rearrange things.
One thing to keep in mind if you're feeling stymied/unappreciated as a writer: it is always harder to do the first cut. If you're trying to figure out if something's a trend or pulling together a technical explanation out of a bunch of different observations, it's sometimes hard to step back and figure out how things best flow together. Or what to cut out. That's why I always have another pair of eyes for my reports - so someone else who isn't as invested in those particular words can decide a newer, better way to phrase things.... As long as they have a specific way to phrase things.