I recently asked a question on how to find a TA. However, I always book a cruise directly with the cruise line. The only reason I inquired about finding a TA is if we decided to go on a transatlantic cruise, we would definitely want a TA to make all travel arrangements from flights, hotels, and the cruise. They know which areas are considered to be safe and special tours.
Therefore, IMO, I would only book through a travel agency if I were traveling to an airport out of our country. For cruises departing the U.S., I would deal directly with the cruise line.