The original Bungie plan was to have the Community playlists be the incubator for maps. Community selections would go there first, more maps could be thrown in since they'd only be up for a week (so no need to worry if a map had some sort of glitch or problem - it'd be gone in a couple of days anyway).
The transition happened, and Bungie had to kill the Community playlist concept and started putting maps directly into matchmaking near the end, because their last updates were basically with the mindset "if Reach never gets updated again, we're at least going to give the existing playlists updates for when it goes into autopilot", since nobody knew what 343 was going to do with Reach after the handoff. This is about the point the submissions became mostly CC instead of Forgetacular submissions.
It could have maybe been done under 343's watch but their Anniversary update put Reach at the playlist cap, and honestly, it didn't seem like they were given the bandwidth to create Community playlists every month judging by the updates we got. Instead of precision changes, changes became universal and heavy handed, globally applied.
- Instead of beta testing TU changes like they originally said, the TU settings were pushed into the entirety of matchmaking, and all the changes were included at the same time.
- Initially, we had the problem where you didn't know what pistol you had in a gametype until you tried to kill someone with it. At this point, people had a choice between TU and non-TU within the same lists. People asked them to label the gametypes. 343 did this. And then made playlists globally TU or non TU at the same time, defeating the point of labeling the gametypes.
- Instead of altering loadouts at the playlist level, Evade was simply removed from every single playlist. Including Action Sack. Which had gametypes that were made with Evade in mind. In Invasion Skirmish, this resulted (and is still like this) in your loadout progression going backwards, because the Evade loadout had the AR in the first phase and the DMR in the second, so now it goes DMR -> AR. Since it was "Take Evade off Spartans", Elites retain their extra loadouts since they retain Evade in Invasion Skirmish.