Oh hi! I played XI from release until recently (with some breaks). IMHO the original story (basically up to Rank 6 where you defeat the Shadow Lord) is fine, but it’s really more of a prelude and setting up the stakes. If you stop there it’s not really worth your time.

Rise of the Zilart and Chains of Promathia (+ optionally Apocalypse Nigh) are pretty good from a story perspective. These can be completed solo. This is what I’d recommend playing through to anyone interested in the real story.

From there it’s somewhat diminishing returns. Treasures and Wings add some interesting bits to the lore. Rhapsody is actually great but will take a lot of time and effort and is probably only worth it to a die hard fan.