I remember when it seemed the most exciting music on the planet.I think it was kinda over-revived, we heard rare groove via a thousand bad student nights and cheap compilations and that just soiled it. I'd class Funkadelic as separate as they never really got brought back in the same way, and their records have enough going on maintain interest.
Thinking about it, I think where funk loses out is the separation of the vocal. So many of the big funk tunes are instrumentals, but the vocals connect with that wider black music legacy - gospel, soul etc.