There is a thing called economy and GDP. BRICS are all in the top 20 world economies with China at US$13 trillion. India $3 trillion. Russia above US$2 trillion and Brazil and Saudi Arabia close to Russia. Guyana...ranking 137th with only US$100 billion. Also, corruption index is a thing.

Why? The five main nations in BRICS have mutually incompatible national aims and will never prosper together or agree on anything except perhaps a common dislike of another alliance. By recruiting smaller partners, all they will do is allow for the formation of mini voting blocs within BRICS itself and further underscore how pointless the idea must be. It's like a five-headed scorpion with about 18 legs trying to swallow a giant anaconda. It's own tail is it's eventual destruction.