Thats one of the oddities of the early MMOs. Take UO for example, UO felt less like a job than any of the newer MMOs I played. Even though it was essentially like all those points listed earlier.
Why? Well one simple reason, people then played at their own pace. Nobody cared if it took 12 months to max a skill, they just played the game and let the skill rise through use. People werent obsessed with getting maxxed as quickly as possible, people werent obsessed with being the first or quickest to do something. People werent obsessed with having the latest piece of loot. Somewhere along the line that changed in the MMO world, the people changed. They stopped playing the games for the enjoyment of them and started playing them for the achievement of them.