The worst part about agile is it has become whatever each company wants it to be. Product owners dominate the pace and direction of development often to the detriment of engineering quality. At least in waterfall model, there is some one like a program manager or delivery manager taking overall responsibility for delivery and coordinating dates with stakeholders. With agile and scrum, there is no one taking responsibility for achieving things. Often product owners end up doing this for which they might or might not qualify for.