You do realise that the servers are still not stable? They didnt even publish their duel gamemode, so they probably got engine problems when creating new game modes or some other issues.
Ranked gamemode is litterly already done, they just need to add UI and icons on top of the mmr system.
Usually Ranked modes have two components: Rank and MMR. They're separate for a number of reasons, but the main reason is to balance each other out.
I assume TW is implementing this as well, where Rank is separate from hidden MMR. That needs UI, assets, and other stuff created first.
Of course, I just want to know how potato my MMR is in Skirmish, but I doubt we'll ever be seeing MMR values.