You can't say they have not used ideas from FFXI in this game. As you can see, they do not work as intended out the door. Both games are completely different from each other and what works in one may not work in the other. You don't understand how a system like you propose works in a new player perspective and an end game one in terms of horizontal progression. Making content like that does not work with the raiding scene in terms of balance, it makes it overwhelming for people getting into end game for the first time, the amount of content has to be very limited in comparison to what we get currently, and developers constantly have to check balance in other gear. It is a confusing mess for this game.
It worked in FFXI because it was built from the ground up with the system in mind. FFXI is also almost all open world content, one that a lot of times require a big group to take down. You think just flipping the switch in FFXIV will just make everything magically work because another game built on completely different concepts did it right (kind of). Can even argue that FFXI, while a fun game in it's prime, was a heavily flawed game in it's design and the rose tinted glasses may be getting in the way of you properly analyzing and comparing the structure of the two games.
Some should ask themselves, are they truly tired of a gear treadmill setup, or are they just getting sick of SE going about the same routine to obtain them? Maybe you should offer a way to make it more fun instead of trying to convince them to drastically alter the system to the point that it is a revamp.
I know I am going to rustle some jimmies here, but I actually like having new goals to set upon every six months. I like taking on new challenges at the pace SE is giving us. Not do the same exact content for years to get one item that never drops. Gear to me is but a means to improve myself to get the content done. Then I can worry about my glamour afterwards. It is just the structure I enjoy. You can disagree, but I believe it keeps the game refreshing. Assuming developers make it fun, creative, and balanced. Those three things is what SE is having trouble with lately.
It isn't the system that is the problem, it is just SE lack of understanding the balance of this game's structure, or understanding the community on a casual, midcore, and a hardcore level.