Spoiler alert.

So I am gonna get straight into it. I will also show how plot reliant the kimetsunoyaiba can get.

Muzan did a very bad thing by sending akaza to the mugen train. He was the worst possible upper rank to be sent there. A close range fighter. If he had sent someone else- let's say doma. Doma is a long range attacker. It is also probable that tanjiro and inosuke would have died between their clashes, assuming rengoku is not able to protect them.

Now send kokushibo. He again can use long range attacks by using crescent projectiles. Same outcome

The same goes with hantengu. Rengoku would not be enough to deal with him. Rengoku would have to fight zohatuken while finding the real body.

Now another misplacement was swordsmith village. Doma wanted to go there but muzan did not send him. If doma had gone to swordsmith village ,likely misturi and muichro would have died,and tanjiro,nezuko and genya also. Let's say doma stays alive and the hashiras,genya and tanjiro nezuko survive,and doma escapes by inflicting heavy damage on everyone. The main premise here is not the fact that SV is still there or not. The thing I wanna refer to is hantengu's survival.

Hantengu + nakime could have been the best BDA combo for the demons. Like imagine in the IC,not only the corps have to deal with 2 extra upper moons,but imagine trying to find hantengu's real body in the IC. That would a fucking nightmare. Nakime would just use her BDA to take hantengu far from the slayers as zohatuken deals with them. This is genuinely the worst case scenario for slayers. **THIS LITERALLY COULD HAVE BEEN THE CASE FOR DEMON'S VICTORY**

These 2 just show how bad muzan is at leadership and strategy. And how badly kimetsunoyaiba depends on plot.