It has now been 10 years since FFXI's release, and many of those players -- who now make up the majority of the FFXIV base -- have aged, have jobs, families, etc. and cannot devote even remotely the same amount of time to a MMO.

In addition, FFXI is still running as a hardcore timesink game (albeit, it's changed a lot since the Abyssea). So it is in SE's best interest to have FFXIV not compete with it's younger sister.

These realities are what has shaped FFXIV into a more casual friendly game. The essential parts of the game (leveling, missions, job quests, etc) are geared towards casual players, but there are other parts such as Achievements, DoL/DoH, Raid Gear sets and Primal drops (depending on luck) which can take a very long time to obtain.

That said, unless you have all jobs to 50, all primal weapons. multiple Crafting/Gathering Jobs maxed, and full Darklight, etc, etc... you still have lots of 'hardcore' stuff to do in FFXIV. If you do have all that stuff and are still bored, then FFXI might be more your style.