It doesn't make any sense for there to be massive gaps between the base hashira
Like the narrative is telling us the hashira as a group, not any one person (except Gyomei) are the strongest, and there is a clear "hashira level" that Giyu has in mind in ICA when he compliments Tanjiro (marked Tanjiro is base hashira level btw). If you ignore that you will get ridiculous conclusions like the other hashira were actually able to low diff GyuDaki and the one guy who would be pushed to extreme diff just happened to be in EDA. Which takes away all the stakes because after that Obanai would just pull up and fodderise GyuDaki if this scaling was really accurate. Why was Ubuyashiki and the Corps unable to kill the UM for a century if they were actually fodder who can be easily killed by any hashira? Why is Tengen even a hashira if he is like a blitz tier below the rest of them?
Anyway enough about Tengen let's move on to Sanemi. This guy is so glazed because he fought Kokushibo for a bit, people act like he is able to blitz marked hashiras and every other kizuki in base form. The story tells us Sanemi is at least matched by Muichiro and Giyu (because...he sparred equally with them in HTA). If base hashira can be stronger than marked hashira what's even the point of the mark? Are the hashira aware that some of them can easily blitz UMs while others are barely above lower moon level?
Unless you have base Sanemi = marked Sanemi it's a foregone conclusion that Kokushibo was holding back during the first part of the fight. He is holding back to an unquantifiable extent so don't act like Sanemi is a perception blitz tier above Muichiro or something like that. It doesn't make sense that Sanemi trains and pushes his limits by sparring with a guy who he could easily blitz at any time.
Note I have not said anything about Gyomei because he is the goat
Yes Doma was holding back against Shinobu he didn't even use half of his arsenal and he is a BDA based fighter. Doma just has bad stats for a UM but it is made up by his broken BDA. Remember in the past Doma was UM6 so according to some people that means he would be perception blitzed and low diffed by almost all hashira, he must have gone on a training arc or something. Because people would rather die than admit UM ranks don't mean you are automatically superior to everyone below you in every stat.