There's quite a lot of people who have a problem with it.
I'd call myself a Vanguard fanboi, but it was my first MMO, so that always helps. However, I constantly have a chat with other people about how good the game was and this is what I think it boils down to:
a) The amount of PvE content in the game was enough to level multiple characters to max-level and only having to repeat a few main areas here and there. You would level past content because when you went into a dungeon you spent days in there, a week in there... unlike today where you clear it in one night then grind the shit out of it for the next week. Dungeons had wings and they were basically the same as raids are these days. The 'trash' mobs were harder than the bosses are in MMO's today. You wouldn't do a whole dungeon in one night, it would just take too long.
b) Difficulty = Time. When you run a dungeon and you have to pick the perfect moment to pull mobs due to multiple pathing packs it makes the game more difficult. That ONE extra mob was the difference between living or dying. Make things more difficult and you add time to a game.
c) Corpse Runs. While I don't think that putting in full-loot drop is the answer to MMO's, even though I have no issues with it, it also added time factor to MMO's. If you dropped your cash, it was always worth trying to get your corpse again. This adds time to the length of any MMO.
d) Mob respawn. One thing that 90% of MMO's lack these days is mob respawn. People just run into fights without thinking because they know if they die it's a 2-minute turnaround to being back where they were up against the same pack of mobs with a better idea of how to kill them. How boring. I recall having to push through a dungeon at a quick pace in Vanguard because if you didn't you got mob respawn behind you and could die quite easily. I do agree that there's a level of 'too fast' when it comes to mobs respawning, but it's a part of MMO's that's really missing these days. This adds time to MMO's because you need to run the content again if you die.
e) Huge worlds. Every MMO comes along and says they have the biggest world. I still can't remember one as big as Vanguard yet.
f) No swift travel. This one crosses over onto the awesome PvP area. In Vanguard, at the start, there was NO swift travel. You went off adventuring like you should in an RPG. You had a horse for faster movement, boats were available with plenty of rivers to go down, but you couldn't zap halfway across the world unless you had bound yourself there. However, at the start PvP also had a rule that unless you got resurrected, you had to rez at your bind stone, which could be hours away. They changed this afterwards and it kinda ruined world PvP because people died, respawned at the closest bind stone and ran back into the fight with full health. Either way, no swift travel added time to an MMO whilst adding extremely awesome additions at the same time.
g) Open World Dungeons. This was by far the most exciting part of Vanguard for me. When fighting a group of mobs you had someone listening to what was happening behind you in case another group was trying to run the dungeon at the same time as you. It created the best PvP fun, whether you got ganked or whether you were ganking, it creates guild rivalry and most of all it added time to the game because you didn't get through the dungeon unphased like in todays games. You might be taken down 3/4 of the way in by a stealth group, you might have to wait 5 minutes till you had some respawn behind you, etc. I'm yet to see anyone bring this to the table since Vanguard... or not in anything I've played anyway. I think Age of Conan had one or two dungeons in the main city that had this and it was great fun.
The summary is that you're absolutely right. Games go too quickly these days, but I don't believe it's because they don't necessarily have enough content, but more about how they actually design the game around that content. Vanguard was setup with a bit of difficulty that people just don't stand for today.
MMO players today, or more the new generation of teens/young-adults coming through don't like to work in real life, want everything handed to them for nothing and that reflects exactly how they are in MMO's and what they want in their games. When MMO's take 5 years to make and 1-2 months to get used and tossed away, developers will soon start to realise that it's not worth it. We're now seeing the trend of developers going back to the sandbox model and only seeing these games start to come out now, or are in development because they've realise that MMO's are going down the shitter and if they don't change things up again then their game will fail miserably.
I think the playerbase is as much to blame as the developers are.