I really like this finale. The struggle is real to stop Muzan from escaping. He even tried going underground of all things on top of that flesh shield. Some real creativity and desperation were shown here by Muzan. This might not even be the end of Muzan's fight, Muzan may have his real body stuck inside the giant baby flesh thing and make a last ditch effort to fight for a minute or two as his body slowly disintegrates. Maybe since he is the progenitor demon, even sunlight won't kill him instantly. I just have a feeling that to make it fit the Shonen feel of the manga, Tanjirou will use some sort of 13th Form finishing technique to defeat his real body. He may need a little bit of help from Nezuko too, if her demon powers still persist for a little while after she turns human/isn't fully human yet.
Muzan has definitely killed a lot of characters in this fight. It might not seem like it, but that's because if he really did kill everyone mid fight it would have spiraled out of control. Many of the Pillars are all bleeding out and pretty much doomed to die of their injuries, and even if they live through the fight, them using the Mark was already a big sacrifice to their lifespans. It all means that if they let Muzan escape here, the whole Demon Slayer Organization will totally collapse and soon later, Muzan would certainly send out some new Upper Moons to mop up whatever was left, as enough of the Pillars would be dead that there would be nothing they can do now that their base has been found. Basically, Muzan escaping is the same for them as them all being defeated by him. It is some really well done high stakes stuff. The only thing he would lose out on would be getting Sun Immunity from Nezuko, but it would still be a permanent loss for the demon slayers and he would proceed in his objectives with little fear of the humans trying to stop him again for a long time.
Another excuse Toyoharu could use to have the battle prolong a little longer in the same way would be if the drug meant to turn Muzan into a human actually worked and turned him human enough that the Sun stopped killing him once it hit his real body, but his Demon powers also began to vanish over time. It could cause an interesting character crisis if he suddenly sensed he was becoming mortal in exchange for being able to fight for a little longer, which to him, would make his whole battle immediately become pointless whether he won or lost. But I think it would be less climactic if he lost the will to fight and was defeated because he stopped giving it his all anymore. Tanjirou will probably beat him with 13th form as he is fighting and burning up from sunlight and etc. I think that whatever Toyoharu goes with will probably be very very good though, this whole manga has really been one of the best Shonen I've read.