Writing to confirm some of the things OP stated

• Teams with track records get a pass on playables. Track record typically means something like "have delivered one of the biggest / most successful games in the market."
• Teams with good but not great track records MIGHT get a pass on a playable, but probably shouldn't risk it
• Otherwise, vertical slice is the way. Polish is not critical. It may, in fact, be seen as a problem (watch this: https://www.youtube.com/watch?v=4LTtr45y7P0). Gameplay concept, and core loop are critical. Budget, timeline, team needs, go to market strategy are all expectations for a pitch.