I wouldn't be concerned. Many reviews tend to highlight the negative, and a good number of these don't give specifics for the low ratings. "The food isn't good," for example, is highly subjective and quite broad. Where did this person eat? The buffet only? Dining room? Le Bistro? Was it inedible, or just not as good as what the reviewer found on other lines? Unless there are specifics, I just gloss over it. (And, I am a review writer myself.)
You're going with the right attitude. Now, if something does seem to be going wrong, bring it to the attention of someone who can do something about it while you're still on the ship. We had such an issue on our last cruise (different cruise line). The dining room service was extraordinarily slow for the first two nights. We left a note for the restaurant manager after breakfast on the third morning (at which service was still very slow), and we noticed a vast improvement from that point on. The restaurant manager also contacted us personally (found us in the dining room, actually).
Honestly, I wouldn't be too worried, although I understand how some reviews can leave that impression.
Happy to answer questions on Norwegian Jewel.