Customization in an RPG is only valid in 2 scenarios: when it's a single player game (such that it doesn't matter that you can make 1 character stronger than the others since you're controlling all of them) or when all of the customization options are explicitly balanced against one another (which is effectively impossible without having an extremely limited number of options; you can only test so much).
In games that use skill trees, they do not offer real customization; they offer the illusion of choice (or, more appropriately, the choice between optimal performance and homogeneity or sub-optimal performance and uniqueness which, in a game where you're playing with others and are expected to be able to carry your own weight, the decision to be sub-optimal isn't viable). As someone pointed out earlier, the only value that skill trees (or any level of "in-depth" customization) add is in the amusement the theorycrafters derive in the first couple of weeks before they've hit upon the most effective build.
Skill trees do not provide "depth". They offer a small period of time where experimentation occurs before the optimal decisions are explicitly laid out. From that point on, unless you're an independent theorycrafter, if you don't read the guides, you're basically shooting yourself in the foot. I've run with people that refuse to read guides and don't do anything to figure out how to optimize their choices; they end up being pariahs because they can't compete or function in a group (and, in some cases, they end up incapable of actually finishing the game because the devs are forced to build around the optimal builds because, without doing so, the optimal builds just steamroll through everything).
ARR made a pretty daring choice that I actually think was the right one: they recognized that skill trees are an inefficient expenditure of developer resources (creating a crapton of options and then making sure they're balanced against one another) so they got rid of them. They basically gave everyone the same "optimal spec" that they would have been using anyways, which freed them up to focus on other more important things (like content, of which there is a crapton compared to other MMOs of similar lifespan, especially horizontal content).
You can say you want customization all you want, but it basically translates into one of two "real" statements: you want to *feel* like there's customization even when there isn't or you want to be different than everyone else and you're willing to make yourself less effective to do so. Neither of those is something the devs should really encourage.