Well, again.. I think the key is balance. Just like itemization, gated content can be exclusionary or so open as to be nearly worthless. In a broad sense, gated content allows structure and prioritization for players, as well as helps reinforce certain gameplay norms that can be beneficial to an MMOs community. In ARR we already have gated content. You aren't able to do dungeons until you've progressed to a point in the storyline. You can't progress to the next tier of content until you've met the goals set for the previous tier. I'm not a huge fan of jumping through 1,000 hoops for something as simple as accessing a new part of a map, or needing a small army to increase my level cap. I think the idea of a true sandbox style MMO, while enticing in theory, introduces a lot of pointless chaos. It not only robs players of a sense of direction but cheapens the entire experience because there's no established standard for performance for content, so everything becomes trivial by proxy.
I think these concepts exist and have existed for a good number of years because there is sound logic behind their rationale. I believe the problem lies more in vastly different forms of implementation. The average MMO playerbase is so polarized that its little wonder developers skew so hard to one extreme or the other. But, no matter what they do, they won't please everyone.
I really believe that having a clear cut progression structure that encourages and rewards player proficiency and teamwork is a cornerstone of a strong MMO. Giving players of all skill levels viable options for progressive content is really important. Sadly in the pursuit of pleasing the majority, many developers end up throwing the baby out with the bath water. Again, this is simply my opinion.
