To dethrone the US as the world's leading superpower. I doubt BRICS will take the US' reign anytime soon.
For thousands of years since the first powers emerged, there has never been a unipolar world which is exactly why US regime's reign only lasted 20-30 years and fell apart very quickly. It is also why BRICS was never meant to create a unipolar world. It was meant to go back to what is normal meaning a multipolar world.
Especially with the EU in play. Constant geopolitical tensions in Europe will only strengthen the EU in the long run. The Ukraine war is only the beginning. Already, EU countries promised to spend 5% of their GDP for defense. Will BRICS stand a chance against the EU's military and economic might? Only time will tell.
I wouldn't call it might!
Economically you just said EU is falling apart when you said they are going to massively increase their war expenses which means cutting funds from everything else and pouring billions into war efforts!
Militarily they also have not much to say considering all these money they are taking out of their crisis ridden economy is going to US weapons manufacturers to build them some garbage that is too expensive and doesn't work as it should.