Were progression servers really that popular though in the grand scheme of things? One thing I've never understood about those that want EQ again was, if you want it so bad how come no one flocks to project99 or even EQ which is still different enough from WoW at this point.
There are a ton of factors that decide whether someone will play a game, the two biggest, discreet groups are overall design and technical execution. It's disingenuous to try and filter it down to just design and say "that's it, that's all anyone decides on", when in fact, execution on technical aspects is a HUGE portion of a players perception. How many times have you heard people say "I loved X game, but it ran like dog shit so I couldn't play it?". How a game runs, the UI, stability--there are all just as, or I'd say, more important that the philosophical "vision" of the game.
The fact is, original EQ runs like shit. It's really bad. It's like driving a car without power steering and enough weight on it to nearly break the frame. It really is, from a use control stand point, an immense piece of shit. Yet, despite that, p99 has an active population of over 1k each night. I'm actually amazed by it, it's like watching people who are willing to take a hammer to their balls just for the brief whiff of some rare mechanics.
But the main point is--Blizzards greatest asset, is the technical ability of their designers to create smooth, functional systems. More than anything else? I'd say that technical execution on mechanics is the primary thing that will drive people from a game in the first hour of playing it, and from all the market reports I've seen, that first hour is *critical*. It's the most critical component in determining whether a sub continues. Again, just think about your own experience--if you think a game is dumb, but the UI, controls and general stability are all good, you're probably more willing to see if the game fleshes out and improves. If those things are bad? You're probably simply going to assume the game is bad.
You can't judge games based just on their design goals. You have to judge them by their execution, too. No competitive MMORPG game has been executed well, aside from Eve, for more than a decade. (Note, quite a few competitive MMO's have been executed well, and they are wildly popular, LoL, WoT ect). Say what you want about WoW, playing WoW after EQ was like driving a BMW after getting out of a pinto, everything about it was just functional and smooth, it was a great experience.