I still don't know why everyone is defending the retainer system.

Everything the devs will do with this system to make it more user friendly or intuitive will turn out to be extremely roundabout or awkward, because the base design of "NPCs selling your stuff in a separate zone like bazaars" is a bad design. There is nothing that this system does, that a system without retainers couldn't do better, easier, and for cheaper in terms of development costs.

Just because you can work with a system doesn't mean it's a GOOD one. SE pretty much spent extra effort to make a system that's WORSE than systems already available on other MMOs (including their own).