During a few of those mergers, server capacity was increased. We don't have numbers or anything, but what was once "high" or "medium" pop is not what it was when the game launched. So while servers may have contracted by 85%, the playerbase has not.
As for population, http://www.riftstatus.com/ shows servers pretty consistently bouncing between medium at non-peak hours (with a few lows) and high during peak times.
Except the MMO genre is still growing both in terms of playerbase and revenue? Yeah...except that.
See above statement. Despite WoW shrinking, the MMO genre as a whole is growing. Not sure what kind of myopic view you're taking of the industry, because it does not sync up with reality.
Vanguard was anything but a copycat. If you think it was a copycat, then you clearly never played it. Vanguard was the most ambitious MMO to launch in the past decade in terms of its scope.
As for Rift/Aion, neither of those are dead. Aion is still chugging along as usual in the West, and Rift is doing pretty well on its own ($36M in revenue last year). Unless your using some kind of subjective, completely meaningless definition of "dead" akin to "isn't as big as WoW", in which case...yeah.
Why not?
I'll be sure to tell that to LOTRO (generated $130ish million last year), Tera ($300ish million last year), SWTOR ($160ish million last year) and the host of other F2P MMO's that have been stable and strongly supported for years.
Meanwhile, the biggest subscription based MMO in the world, one generating over $1 billion annually, has a live client abandoned for 14 months. None of the major F2P Western MMO's have ever had a content drought that long, not even Champions Online (which barely sees any support).
You're free to play and enjoy what you like, I'm not one to tell you what to do. But to call F2P games "semi-full" is pretty false. There are plenty of them that gate little to nothing off from free players, and most that do gate off content/features provide those as part of an optional subscription.