Singapore is a huge container port so you need the shuttle bus to at least get out of the place. We had a complimentary tour of Singapore before arriving at the ship but it is a place worth visiting and is easy to get around
You dock at a purpose built cruise terminal and there is nothing there so you need a trip, taxi or shuttle service. However the shuttle only went to a shopping mall. Our trip A Glimse of KL gave us a good overview of the place and several stops for photo opportunities. Whilst stall holders would accept Us dollars and euros you need local currency to use the public toliets here.
The ship docks on a pier which seems to be in the middle of nowhere. The shuttle takes you to the nearest resort where there is a public beach and a few shops. Our trip visited a rice museum then took us to a cable car for a view over the island. There were long queues here and when we reached the top it was misty so the view wasn't that good. This was an expensive trip for what was included. The next two ports were Maritius and Reunion we did not take trips at either of these but wish we had. We didn't see anything of the islands. The shuttle service at Maritius was to a tourist water front with shops it was 5 mins away as the crow flies but 30 minutes by bus. At Reunion it was to a small beach resort.