As much as I dislike SkyTeam's China member airlines (though CZ and Xiamen Airlines are borderline okay these days), I think you might be underestimating their collective power in the market.

I almost never make connections of any sort which entail Chinese airlines, let alone domestic to international at PEK/SHA/CAN, but the fact of the matter is that I end up spending a lot of time on CZ, MU, FM, Xiamen Airlines, and KN (China United Airlines) because, collectively, their market share is nothing short of dominant. And, take Shanghai, for example. Now that HO (Juneyao Airlines is putting MU/FM/CZ codes on most of its flights), Skyteam is sitting pretty. On my SHA-NNG route that I fly 2-4x/month, the only non-Skyteam option is Spring Airlines, whose seats are seriously uncomfortable.

Skyteam has a similar lock on CAN, and is competitive in BJS, especially if you include KN in the mix, which I don't think is a full SkyTeam member.

That having been said, one could argue that alliance participation (at least among Chinese carriers) is increasingly meaningless because the percentage of mileage earning fares on many routes is in the single digits. (I typically book the lowest available revenue fare class 2-3 days out, and am lucky to earn 50% miles. Sure, I could spend an extra $70 to earn 1,000/1,600 mi/km, but this isn't a compelling value proposition for me.)