Firstly the new playlist update is stripping away the ranked experience. We really dont need that. The playlists we do need are:
4v4 Arena (Open) - Slayer, CTF, Oddball, King of the Hill, Strongholds
2v2 Doubles - Slayer, CTF, Oddball
6 Player FFA - Slayer (8 Player is not good for ranked)
Rotating Playlist: Survivors, Team Snipers, FFA Snipers, Tactical Slayer, etc.
We dont need the solo/duo playlist if there are a FFA and 2v2 playlist. Having a rotating playlist is great but that doesnt mean we should lose 2 staple playlists for it. Ranked needs to offer that variety, we dont need to lose it just because population is low RIGHT NOW (population across the whole game is low so not a good reason to remove these staple ranked playlists).
Furthermore we need more incentives to play ranked, eg:
Champ Rank (Top 200 CSR players)
More ranked unlocks (Coatings, nameplates, armour pieces, etc.)
The rank system and matchmaking could also be better. It felt a lot better in Halo 5 so that could be a good place to start.