I heard that lot of people from final fantasy 11 quit and move on to different game or FF14 not sure if the community is large as back then 2004-2006.
Yeah, but SE consolidated the servers to help make up for that. (Trust me, with how crowded endgame is, 2,000 people on a single server at primetime is more than enough.) They also adjusted nearly every aspect of gameplay from level 1 on up. Exp? Can be done solo til 20, at which point you exp in an alliance til 99. That means no fighting over exp camps, no prima donna jobs, and far less gear elitists since exp is fast and easy. Expansion missions? Many can be solo'd by most jobs at level 99. World class weapons? Can be done by you on your own time - you can even more or less solo a relic weapon in Dynamis in a few months if you work at it for a few hours every day now.
I've played XI full time since 2005, and while dunes may be empty, that doesn't mean that Port Jeuno isn't a busy and hopping place.