Nothing wastes time like unproductive discussion. The idea of an unproductive discussion borders on redundancy because so many are.
Discussions are OCD experiences. Time is wasted in the endless banter of opinions, complaints and digressions. We call in all kinds of interesting and frustrating circles and tangents, arguments and distractions. It divides the group into people who love to hear themselves talk and people who want to be anywhere else.
Discussions do not result in deliverables. They typically result in somebody having to go off and do the real work now that we've wasted everyone's time or we reschedule to have more pointless discussions in the insane hopes that more of the same will produce different results.
The opposite is a work session. These feature questions, planning and decisions. These keep converations focused, engaging and productive. This is new for most people, so they have to be exposed to it in order to become contributors, When people bring in opinions, complaints and digression, we do what we can to reframe them into work session relevance.
The difference is in the design of the process. It is actually simpler to have a working conversation and infinitely more satisfying.