I'd rather say Miko is more "cunning", not simply smart.
Not being picky with her methods is a powerful trait for strategists, but it has its drawbacks. Being unpopular for example, in-universe or in the fandom.
And like >>13543614 said, Byakuren isn't "brawn over brain" stupid, she's just more careful with her approach, and tend to pick a way that won't drag along unnecessary bystanders/innocents.
Also, I don't know if it's just me, but she's the type that'll take care of stuffs herself, rather than asking others to do it for her. The reason Mamizou came is only because Nue called her without Byakuren's permission. And since they can't prevent Miko from breaking the seal, she'd rather meet her in person before taking any actions. So, talk first, then decide.
Saying that they're weak or don't have enough "quality" is kind of a weird statement, though.
Remember that Ichirin and Unzan is already a match for Futo, while Murasa and Shou(with pagoda) is about the same strength, if not stronger. Not to mention there's Nue, and Mamizou is still arguably on their side.
True enough, the Taoists have an edge in strategical play, but in a 1-on-1 fights, things may be different. Also, remember that Byakuren's followers have a different kind of loyalty compared to Miko's. These kind of bonds have special qualities that some simple orders or tactics cannot accomplish.
Add Yuyuko's group as well. She is after all, a Buddhist nun too. Was, perhaps but she still follows some of the teachings.