I like your distinction between playoff and invitational tournament. Let me expand on that...
For me to take it seriously as a playoff, it would have to be setup like other NCAA Tournaments where conference champions get an automatic berth. This would discourage all of the ridiculous conference consolidation and ensure that, from the start of the season, everyone has a legit shot of winning the title (however stretched those odds may be).
The fact that the ACC Champion (Duke) was excluded while a team not even eligible to play in its conference championship game got into the "invitational tournament" is ridiculous, regardless of other logical justifications.