Flying Fish is far and away my favorite on-property restaurant for the food, and I’ve eaten there solo several times. The Boardwalk area is very pleasant, and the adjacent Abra Cadada bar is also fun and cool. However, Flying Fish is not cheap so check the prices to see if they suit you.
The choices others have mentioned above are also enjoyable. Another option not mentioned is California Grill. It’s in an iconic location on top of the Contemporary and a great experience; try to time your reservation so as to enjoy the view of the fireworks from the viewing platform. As a single, you probably won’t be seated at a window table, though, because if I recall correctly, those are all four-tops and the two-tops are not directly next to the windows.
Although I ate several years ago at a restaurant in the Monsieur Paul space, which might have been been Bistro de Paris at the time, and was disappointed. However, based on the comments above, the restaurant may have been reimagined and be much better now. Worth some additional checking if that option interests you.