I agreed, but I'm not sure a warning would be sufficient. I thought W screwed up in not going into Bora Bora at the onset, once they refused to hand over OBL, but that was a tactical decision to not have casualties, so no hindsight from me.
I thought the drone war was necessary. Our armed forces killed all Taliban leadership and forced the Taliban to Pak to regroup. Maybe that was 2002, I don't remember. But after our military accomplished that, imo it was mission accomplished, although staying on to kill OBL was not, imo, a waste.