I was in from beta until about 2004. Lots of fond memories! Closest I've come to feeling the same way I felt playing AC in recent memory is actually Valheim. Can't quite put a finger on why, but there are very few games that hold such an important place in my heart. I was a high schooler when it came out. Some days I regret not going into game design, especially with the current wave of VR games. Some days I'm tempted to quit my major tech company job and try to create that magic myself in a VR MMO.
But that would be something only a crazy person would do.