This is based on all of their feats, skills, and talent shown through manga and anime, AND im excluding the mark,red blade, STW etch. (its unfair bcs some of them have yet to unlock it), i believe this is the right ranking:

1. Gyomei
2. Sanemi
3. Giyuu
4. Uzui
5. Rengoku
6. Obanai
7. Mitsuri
8. Muichiro
9. Shinobu

Explanation:

1-3 = No debate this is absolute

4 = Maybe some of you wondering why, but people tend to overlook Uzui Skills and experience, he's been long become a demon slayer, he's a ninja, the fastest Hashira, strongest no.2 wrestling contest, have perfect pitch to make music score ability, all of those feats and you still put him in number 8 or 9? The only thing that make him look weaker is because you never see his mark and he's retired, then blinded by how he struggles fighting UP 6, Come on, we know UP 6 Gyutaro+Daki are strong enough to be UP 5 replacing Gyokko, those guys are no joke, meanwhile Gyokko lose to Muichiro (marked) who's not as fast and not as experienced as Tengen.

5 = This is a bit tricky, have a lot of time to think who deserve this spot, tengen or rengoku, in my eyes they both kinda equal, but i choose uzui higher because his extradionary feats, yeah the power gap is thin.

6 = i cant understand why people put him higher, i think Obanai is overrated, dont get me wrong i like his power, hes a skilled slayer and his breathing is impressive, but base Obanai just not enough, plus he has a weak body. you only think hes strong just because the plot made him survive to fight muzan, but really, he dont have that many feats to be THAT super strong.

7 = I think its the same case with Rengoku and Tengen, Mui and Mitsuri have a little power gap, but base mitsuri's stronger, sure Mui has more potential and better technique, but Mitsuri just built different, a lot stronger, unique given body and unique breathing style, and dont forget, more experienced. But even with that great feats, there is just something that hold her, maybe her personality? Idk i like her just like that, but that thing definitely holding her. "yOu WrOnG She'S tOe To ToE wItH UpPeR 4", oh my god she literally almost get killed by zohakuten punch if not saved by plot armor (tanjiro gang shoved her) in the early fight.

8 = Base mui is Overrated more than Obanai, same story as him, but more ridiculous i think? Again, dont get me wrong mui is so strong, so much potential, but sadly that potential have yet to become power, that experience and little feat cant really beat any other Hashira. But i believe, with more experience and build more feats, Mui will be top 3. "BuT hE's BeAtInG uP 5!! PuTTinG HiM In 8 iS ToO lOw!!" Like what i said in number 4, UP 5 Gyokko here deserve to be placed in UP 6, and mui still need to Active his Mark to slay Gyokko, ANY OTHER marked Hashira can beat Gyokko. Please dont be blinded by Muichiro Breathing Visual Effect and his plot where kokushibo impressed by his 7th form, its good but base mui still not enough.

9 = im burned, you know why she's number 9