The game was released buggy, like many MMOS, but at the same time, the devs tended to be receptive to feedback. That said, the game underperformed by a lot. Sales numbers were not as predicted or hoped for, and the number of subscribers retained dipped very low.
The game had a ton of faults, and a lot of missed potential, but when it comes to who dropped the ball I would have to place more blame on Monolith/WBIE for selling the property off to SOE. Now that said, SOE put effort into the game but it was never treated as a star property. One might say, with good reason, noting the underperforming history as above. They had to keep profitable.
But MxO was Monolith's baby and the devs and designers there worked hard on it. They had a good strategy and a plan for afterward, and the first four or five months after release were truly great stuff. Live Events were plentiful, characters would drop in, there were very effective storytelling elements in place and fairly frequent updates. The events that they held and the LET appearances really helped tie the community together.One really felt like a part of something. But of course, back to those numbers again -- it very likely wasn't financially sustainable.
The sale to SOE gave the game a longer life, but also a slow death. Fully rendered cinematics with original cast voices gave way to comic book format animation and finally to some drawn, barely animated storyboards that were hard to make out. Major characters were killed off or otherwise removed (likely as a way to save money), and only little things were added to the game. This was mostly in the form of gear or spawns of some sort.
I doubt there will be another like it for some time -- urban, smart, featuring an abundance of modern clothing options and styles, and filled with a mix of philosophy, supernatural elements, lots of places to enter and secrets to uncover, and a very unique playerbase full of extremely dedicated individuals. And in the beginning, the Live Events team played it well, and created the most memorable MMORPG experience I have had so far. It was fun, but sadly, the game did not realize its potential at all.