Actually, nowadays it's very soloable: you can experience all of the story by yourself thanks to the Trust system. I only recently tried it, and control scheme wasn't as bad as I expected (but you do need some patience). From what I gather you don't really need to learn about macros and gear swapping mid fight in order to clear story content.

In addition to the community-aspects others have noted, the combat system is a bit slower-paced and extremely strategic. The jobs(classes) are all extremely unique and the sub-job system allows you to play them differently as needed. You can switch jobs on one character so you really grow attached to your specific character rather than making different characters for different classes.

You can swap-gear mid combat which gives you a lot of situational flexibility that makes it feel like you're actively contributing to your success or failure. As an example you might have a set of great for a specific ability, or switch to defensive gear if you draw the enemy's attention.

Additionally, the story is really nuanced and the side-characters are often very realistic in their choices, motivations, and there is a sense of consistency throughout the world that really makes it feel "lived-in" in a way a lot of other MMOs don't bother with.

Honestly I could go on and on. It's just a really special world and will stick with me for life. Even a few years out from playing I still get the itch to go back constantly. Vana'diel is like a second home for me.

You had to team up to accomplish anything, so it was easy to make friends. The game also had zero handholding, which made it incredibly immersive. You can still experience the game as it was in 2004 on the private server HorizonXI. It's popular and has thousands of people online at all times.