I think the Pirate Legend is fine, The game isn't supposed to be done within a couple of weeks it's there to work towards over many years, I mean they could make it easier to get and rename it to "Pirate Apprentice" but becoming a pirate Legend is supposed to take time and effort fitting of the title and I'm sure when people hit it it's a nice feeling of accomplishment and joy.
I do expect some of the events in the future to include double gold/rep weeks or weekends for a specific faction that rotate every few weeks to help boost people and encourage them to do voyages for different factions.
The only thing they need to change are the achievements for 1,000 banana, wooden planks and cannon ball crates etc really as they are just stupidly high or they are intended for a future mechanic/feature that isn't implemented yet, Also over years SoT will likely keep adding new achievements and the game will likely end up well into 3000-5000 range.