Let me join this discussion to make things more clear.
I don't intend to write too many lines about GB's history, its main goal and policy but I'd like to mention one important thing.
GB is basically a non-flashing custom ROM which primary goal is to bring custom-rom like experience to closed-source platforms (like MediaTek) which currently don't have opportunity to have custom ROMs built from source.
Later while evolved, the secondary goal was established - to bring custom-rom like experience to devices running stock Android.
What I see happening around Xposed Framework recently is that people are basically often turn to using it to "patch" what they can't find in a custom ROM. However, Xposed modules (especially the complex ones) should not be used to supplement missing features in custom ROMs built from source. The best option for a user is to go ask devs of the custom ROM he uses and request those missing features. (This is also clearly mentioned in GB's official thread). People don't combine two ROMs in one device to get more features, neither (thanks god it's not possible!)
GB is not here to keep track of what's changing in all custom ROMs available out there. It is simply unmanageable. GB is here to extend the stock Android experience just like any other custom ROM does.
And words like "GB can't keep up pace with KitKat" sound funny. Actually, it keeps up with stock KitKat pretty well.
I understand these words come from people who have zero experience with GB, but anyway.
GB is currently fully compatible with the latest stock KitKat and is even bringing Dialer tweaks in upcoming version which none of custom ROMs have to this day (flip actions, call vibrations, etc.).
