Who said it was rotational?
It's literally in the first post:
This list will start as a rotational and whether we keep it permanently will depend on how well it does.
Personally I think Ranked should strictly be competitive only options. Look at any other game (CSGO, RS6, LoL, SC2, Overwatchetc) found in eSports that has RANKED matchmaking... it is the same deal; it is because the settings are the most balanced for competitive play, whether players like it or not.
This should be the new matchmaking system from Day 1 for Halo: Infinite and what remains of Halo 5: Guardians:
Ranked
Team Arena (HCS 4v4 Settings)
Doubles (2v2 Settings)
Free-For-All (HCS Settings w/Kill Cap)
Rotational: Snipers etc.
Social
Big Team Battle (8v8 Settings)
Team Social (4v4 Settings - Slayer, Capture the Flag, Strongholds, KOTH, Assault, Dominion, Extraction, Oddball, Ricochet etc.)
Infection (Infection settings)
Rotational: Grifball etc.
We strictly DO NOT have a sustainable population anymore in the Halo Franchise due to people having different likes and dislikes which can be catered for with the different types of games on the market today etc. It is not the matter of making X great again, it simply is fact and we should come to terms with it... we just need to figure out how to optimize matchmaking search times, region connections etc. Directing more players into groups will accomplish this...