Rums tend to be sweet since they are made from molasses or sugar cane (rhum agricoles). They often have added sugar after fermentation is complete, especially mass marketed rums like Captain Morgan. read more
So, sugar and spice and alcohol make Captain Morgan's a very delicious drink all by itself. If you are used to drinking single malt scotch or any other spirits neat, Captain Morgan's might seem too sweet. read more
The biggest problem I have with Captain Morgan is that the rum it is most similar to, Pussers is just so so much better. Captain Morgan is nothing like the sickly sweet “navy” rums such as Skipper and Lambs. read more