I had this happen to me once. I told the party I'm leaving if that person doesn't start playing. It's not possible to start a dungeon and be afk, you have to ready up to be put in so they aren't just "whoops sorry I was afk" they are just not participating and that means that kicking them if they stand still won't do anything. When this happend in my party I saw his status in the party list go from normal to watching cutscene back to normal, so they were there and skipped the cutscene.
Glad to see your aware that it's an issue but the proposed solution won't fix anything