I think its about what you want to do. I have been on an Alaskan Disney Cruise twice and going on a 3rd later this summer. I would go alone if I wanted to. There is so much to do and see.

The only time I wouldnt want to be alone is for dinner. You have rotational dining and you sit a table with your family or who ever you are with. So being alone might not be that fun.

When I went the first time I happened to find out that some relatives were also going so we got set up for our families to all have dinner together.