Endgame is a huge time sink, and a lot of it can't be regularly scheduled. If you decide that you want to experience it, you have to understand that it will take up most of your on line time. For some people it's worth the commitment, for some people it isn't. Endgame shells do need people who will spend most of their time in shell though.
Runs that can be regularly scheduled though, like Dynamis, Limbus, assault, BCNMs etc still let you experience some of the endgame stuff, without making such a large comittment, and there are a lot of smaller shells (often aligned with the larger shells) that let you try out endgame.