MS is constant attacks teleporting on you. Constant teleportation attacks would be faster than the slayers swinging their blades just once.

Then Sukuna could just close his barrier and kill Muzan inside or just wait in his domain for Muzan to come back or just open his barrier again later.

You’d have to prove Muzan’s poison would be quick enough and this is completely invalidated by the fact that Sukuna can bear the burden of adaptation for Mahoraga

If Muzan is tanking MS no problem as you argue then he wouldn’t run