It's a war and WB could destroy the whole place because of his DF. Akainu obviously won't try to cover the whole place with magma so yes 3 of them were to prevent him from destroying the place. When top tiers fight the environment is also in trouble. They were protecting marineford while simultaneous trying to take them down which was clearly not easy. This wasn't the type of battle where admirals could let loose like they wanted. This does not make Yonko > Admirals.
Although the premise you propose sounds good, it ends up being incongruous.
- That you need 3 Yonko, to control 1, is not normal. To control a Yonko you need 1 Yonko.
- Aokiji and Akainu precisely filled everything with ice and fire Lol
You're always going to end up in inconsistencies if you really Admirals = Yonko.
WB was sick but that's not Akainu fault, they exchange a few blows and that's it. Akainu was not gonna come out a fight with someone who may have been stronger than him unscathed. When people say they are equal we are talking about tier. At the end of the day someone will win and someone will lose. Whitebeard was the worlds strongest man, he would beat Akainu but barely, just like how Luffy barely manage to beat Kaido. Admirals vs yonko will always be extreme diff, it took Akainu 11 days to beat Aokiji.
You lack a bit of reading complexion. Of course it's not Akainu's fault that WB is sick.
The point is that if Oda wanted to imply that Admiral = Yonko, he wouldn't have nerfed WB as much. If Akainu had beaten a WB, even if he was old, then we wouldn't have this debate.
Why did Oda weaken Shiro so much?
They need them because the gap between VA and commanders is huge. We all saw how strong Doffy was in comparison to Smoker, the crew of the warlords can balance out the power of the commanders. So if 1 admiral fight 1 yonko the admirals won't need to worry about commanders trying to gang up on them. After this is just fodder army vs fodder army because Kaido gifters were trash, this is why it would take 4 yonko's joining hands against the navy for them to destroy each other.
Again what you say sounds very good, but it is not true.
You're comparing Smoker, who is one of the newest (weakest) Vice Admirals to one of the strongest Shichibukai, it's an unfair comparison.
- I remind you that Garp was a Vice Admiral and was probably the strongest marine.
- Right now, we have Momousagui and Chanton who despite being Vice Admirals have a poser close to Admirals.
- And then there are the Top Vice Admirals like Momonga, Onigumo, Strawberry, Doverman...
We know that there is not much difference between the strongest Admirals and Vice Admirals. So according to your criteria they should be able to deal with the Commanders of a Yonko easy or medium difficulty.
Again the powers are balance, and the marines control the whole OP world except the areas where the yonko reign. The admirals are the navy greatest strength the same way the yonko is the highest pirates. Anyone who thinks the navy has ABSOLUTELY no one to rival a yonko is a fool. Even Roger had issues with the marines in his day and struggles with Garp smh. Obviously the navy is more powerful than ever because they saw it fit to get rid of the warlords.
I agree that the powers should be balanced, but if Admiral = Yonko they are not balanced, not even close.
We have 4 Yonko who are also not together, they do not form a unitary power, against 6 Yonko + the Shichibukai (SSG now) who work together.
The question is why doesn't the Navy send 3 Admirals and a few Vice Admirals to take down the Yonko one by one?
For example, let's take the case of Big Mom.
Sends 3 Admirals (Yonko), one to face Big Mom, another to take care of the Commanders, if Green Bull defeated 2 Commanders easily, without receiving a scratch, I doubt he can't with 3 suffering a little and finally the 3 Admiral with the Vice Admirals who finish off the fodder.
It's easy win according to you, the Admiral who takes care of the fodder should take a few minutes, then he can help with the Commanders and finish them off too quickly and then the 3 Admirals (Yonko) take care of Big Mom easy. Also, in this case we don't have to worry about damage since it is Big Mom's territory and if something unforeseen happens (that a Yonko decides to go crazy), we have another 3 Admirals (Yonko) and the Shichibukai (SSG) + a heap of reserve fodder.
When you finish with Mom, you give them two weeks of vacation and you go for Kuro, then for Shanks and finally for Kaido, who besides being the strongest, is more complicated to reach his territory, but you can already send the 5 Admirals and simple task.
You put it as you put it doesn't fit.