I even have a better argument i found, that i think will shut this case down.
(Not my argument, but still facts.)
Iguro entered fresh against Muzan with no injuries or fatigue of any sort, whereas other Hashira were heavily injured and fatigued from their previous UM fights.
- Giyuu was fatigued, and fought with a broken sword and an almost dead arm(from the Akaza fight) against Muzan.
- Sanemi was fatigued, and injured, missing 2 fingers, and holding his guts with bandages.
- Gyomei was fatigued, cut, and bruised too.
Unmarked Iguro was stronger than Marked Giyuu and marked Sanemi against Muzan, and that's why he was able to perform on their level.
I'll agree Obanai did protect Tanjiro, but he himself was saved 5 times in the final arc.
- He got saved by Yushiro against Nakime
- He and other pillars were saved by low-rank demon slayer where they sacrificed themselves by jumping in front of Muzan's attack.
- He got saved by Zenitsu when he almost fainted
- Probably got saved by Giyuu and Gyomei from Muzan's Shockwave attack(Inosuke comment)
- Tanjiro helped him with Yushiro's talisman.
When Iguro entered the fight against Muzan, he saved Tanjiro and was the 2nd pillar to get a hit on Muzan along with everyone else, but as the fight further progressed, he was ghosted. He, himself mentioned how he has contributed the least in this fight. Iguro had gotten so weak just from fighting Muzan and his poison, that he decided to shield Himejima instead of fighting Muzan, but even that wasn't possible for him.
After Mitsuri got injured, he decided to sacrifice himself. In chapter 188. He stated, " First, I must die and swap out this body that's flowing from impure blood". (and this is the guy who lectured Giyuu for not understanding the role of a pillar)
Iguro did sever Muzan's limbs, but with the help of Sanemi, who created the opening for him.
After getting the antidote for Muzan's blood, Iguro decided to turn the tide around for himself, but he almost fainted right after turning his blade red and was saved by Zenitsu, which shows a lack of strength as well.
In Muzan's Shockwave attack (which took out everyone) Giyuu and Gyomei were the ones who saved everyone around them(Inosuke comment), which cost them their limbs.
Iguro got lucky, as he only lost his eyes. Any lost of limbs, he would've died from blood loss right then and there.
Also, Iguro was already half blind since birth. Kaburamaru was the real MVP, who helped him fight Muzan as he(snake) was predicting all of Muzan's movements. Going full blind had little to no effect on Iguro, as he wasn't that desperate. And anyway, he did get Yushiro's talismans, so he got his vision back as well, making his "blind fight" a question of a chapter.
The version of Muzan, Obanai, and Tanjiro fought for 25 minutes was exceptionally
WEAK in the final hour of the battle(When Tanjiro fought solo against Muzan), probably weaker than his 12 kizukis. As he himself mentioned it " Its unbelievable that I can't instantly kill a man who's so heavily injured. All because of the Tamayo drug. They are not fast, it's me who is getting slow" Muzan was hitting fatigue, he was out of breath, vomiting blood, and running low on stamina, which is not normal for demons, as they have no concept of fatigue and stamina. Even Inosuke and Zenitsu, whose power levels were not close to pillars, and who didn't even have a mark were holding their own against Muzan for the last 25 minutes of the fight.
About STW
Iguro only got to experience STW for like a second before he got taken out along with everyone else.
Just try placing fresh Rengoku or Tengen in place of Iguro in Muzan Fight. They'd perform even better than Iguro at base cose not only they are more experienced, but they also have far better stats than Iguro.
TL;DR Gyomei slams, this thread is a disrespect to our blind boi.
(FYI, Demon slayer characters have Reactive Power levels, while that is true, this hasn't been shown to be permanent. So Gyomei's power amp against kokushibo, or any other hashira being "stronger" permanently by fighting upper moons is out the window.)