I mean he a Marine spy so his goal wasn't to be commander he could be hidden some of his power from kaido
The point is that Yonko crews have a hierarchy - a strict one which has to be adhered to for such large and influential crews and their operations to work cohesively and effectively. These Hierarchy's tender authority in conjunction with power
Captain > YC1 > YC2 > YC3 > Officers
Linlin > Katakuri > Smoothie > Cracker > Snack, Oven, Daifuku, Perospero, Compote, (Capone)
Kaido > King > Queen > Jack > Drake, Sasaki, Who's who, Ulti, Black Maria, Page One
If Drake were a YC2 or equivalent in strength, he would be YC2 or equivalent in authority. This is made evident by the discussions the Tobiroppo have. They talk about taking over from Queen or Jack. It's simple. If one goes, another takes their place. These guys are awarded their position based on merit. If Drake was YC2, he'd be a calamity - if anything that's even more advantageous for a spy - he would have access to more information, authority and say in how Kaido's crew conducts its business.
Lastly, people can be measured using CoO. With CoO one can measure how strong somebody is. Katakuri did it. Rayleigh did it. Are you implying nobody in Kaido's crew can? Because that's a ridiculous notion