CBA is not very competitive, but rather a fun multiplayer mode for casuals.
The RTS genre itself is almost dead, most games with fun SP content are old and therefore hard to measure.
We are talking about different audiences: While the casual multiplayer crowd gathers to make games like Empire Earth, Earth 2150, C&C etc. playable again with various mods, games today all try to cater to e-sports only providing streamlined maps, modes, settings etc.
As I said, ranked players are an actual minority in RTS, it is a different audience. Even if the AOE4 devs were to do weekly balance patches the game would slowly die out, as there is nothing else to do aside from standard ranked matches.