Remember -- the WC was losing the Rampire War.
They had lost so many Wardens & other combat-wizards, they were training up kids as combatants. That is a desperation move, right there.
Then the Ramp's pushed Harry Dresden too far, and it cost them everything.
All of the powerful wizards have a few "OMG" tricks up their sleeves... the Blackstaff showed up with a private army of Kenku, fer cryin' out loud! Not to mention Mother Winter's Walking Stick...
But Dresden arrived with *ALL*THREE*SWORDS*OF*THE*CROSS* . Remember, just *one* Knight with *one* Sword was able to take out a (capital-D) Dragon.
If the Ramp's had just kept up their same campaign, they very-likely would have won; or if not an outright victory, done sufficient damage that other predators would have moved-in and taken their own bites.
And now that the Reds are gone, what remaining faction has the power and the desire to take out the White Council?
The Formor would have the best shot but they are limited by being a mostly water-bound nation. Also, after BG, everyone is at war with them so the Council won't stand alone.
The White Court doesn't do open confrontation and don't really have a need. Nothing they do violates the Laws of Magic.
The Blacks don't really have the power. Drakul can take any one of the Senior Council but any two would be a real fight and three or more might take him. They lack the numbers and they are too vulnerable during the day.
Mab is alternately amused and annoyed by the Council but she sees them as useful tools for her real job. Ditto Titania.
Who else is there? The Denarians are too few plus the KotC will join that fight, the Ghouls lack the numbers and the power, Vadderung is an ally, the Svartalves aren't aggressive, the Jades have never made an appearance and Ferrovax isn't concerned about the world on that level.
The Council is fading fast but they're still a force to be reckoned with. Think of them as the equivalent of Great Britain in the real world. The US and China can take them, and maybe the USSR also but no other country wants to face them even though they're a far cry from the glory days of the British Empire.