I think the one thing that is difficult to convey, in the case of a game like EQ1, was that you were part of a team, that had grown and bonded together through time and challenges.

Even when my role in a boss fight was limited in time (say as 3rd tank in a tank rotation) I was always enjoying the raids because the stakes were high, the people I was raiding with were mates who I cared for. Everything could go downhill very fast and one's ability to improvise when the unexpected happened was paramount. You wanted to make sure you did everything you could for the success of your team and the feeling of accomplishment was amazing. I was never bored.

This is not to say that EQ was perfect, far from it, and newer games have brought some interesting innovations. But to be more accessible, they have also become less immersive and more individual oriented than community / group oriented.