I'm gonna disagree.
I am no where near a "hardcore" player, and I am not a "casual" player.
(As an aside, I'm seriously tired of gamers having to be pigeonholed as either "hardcore" or "casual")
I don't think the problem was that MMO's were too difficult or punishing. I also don't think that making them more "casual" was a solution.
Hear me out.
With the 1st and 2nd generation of MMO's (Ultima Online, Everquest, Asheron's Call, Dark Age of Camelot, Star Wars Galaxies) you didn't create a character and log in for the purpose of completing the game. You logged in to build your character, meet people and make friends, join a guild, explore the world, craft items, open a shop, help build a community, tackle dungeons, hunt down bosses, find treasure, defeat other players from other factions, protect your guildmates from playerkillers, hunt down playerkillers, and generally experience the life of your character.
All of the above was made more fulfilling and gratifying because it took a little bit of work, dedication, and sweat to make it happen.
Very few, if anyone, logged into that first generation of MMO's thinking "Man, I wish I could skip all this boring training and leveling crap so I can beat the final boss and finish this game."
Something happened though, in the transition of that 2nd generation. Developers began spending more time on content at the end-game. Why not? Most of their players were there now and they had to come up with a way to retain them instead of them moving to another game.
As end-game content expanded, it was necessary to up the difficulty in order to keep people playing. If you could clear new content in 1 month with your level capped character, then there was no point in maintaining a subscription. You could buy the expansion, play your month and see all the new things, get the new loot, and then happily suspend your account and play something else until the next expansion.
Fast forward to today's MMO's and what you find is a glorified tutorial designed to take you, on rails, through leveling your character to cap. Because level cap is where the real game is.
You want to defeat the Lich King? No problem. You can have every step from level 1-80 laid out right in front of you so you don't even have to think about what zone to go to and what monsters to fight. Grouping? Not necessary. Even though the game is Massively Multiplayer, you can breeze through the entire leveling experience all by your lonesome in about 5-10 days of play time.
"But you can't defeat the Lich King by just being level 80", you say? No problem, the game has already been modified to allow you to get 75% of the gear you'll need to enter the last raid dungeon without ever having set foot in any of the previous raid dungeons. It's a good thing too, because you won't be able to find anyone doing the previous content that will accept a character that needs the upgrades from that content anyway.
Developers have been making their end-games more "casual" because they're doing nothing to keep players from racing to be there.
No, I think the original MMO's WERE casual games. A typical night in UO could be spent in a guild tavern, doing nothing but sitting around and telling stories with guildmates. In Everquest, the developers knew that not everyone would be level capped and waiting for the next dungeon to be released because they were bored with the latest. There were things to do regardless of your level, size of your guild, and/or your ability to put together a small army of people to tackle a boss. Yes, there were some things that were extreme, including death penalties and week-long respawn timers, but they were doing something new and different and trying different ways of keeping people playing their game.
The major punishments were ironed out later on, but the popularity was growing and the gaming companies wanted to sell more product. The pendulum swung too far in the other direction. The status quo has become so diluted now that anything resembling the original ideal of an online world where you log in to a character and participate in the world just for the experience of the world is laughed at.
Today's MMO's have become a mad dash to the end. A single-player game teasing you with lots of little goodies you'll get to play with when you reach level cap. A glorified forum full of people and guilds waiting to post "First!" when they complete new content.
If you're not having your hand held by quest givers to direct you through the content, your game is a "grindfest".
If you are encouraged to seek out people to form groups to see content before you are level-capped, the game is too "hardcore".
If you can't defeat 3 other players on your own, the game isn't "balanced".
If you want people to experience the world you've built and not worry about being level-capped, having the best gear, a bank full of wealth, and plenty of things to do once you're at level cap, then your game is not only "too easy", or "boring", but it's also "incomplete" and "lacking content".
I still "play" my MMO games. Do you?
Or do you "complete" them?