It should be understood that Kinemon (+3 scabbard) jumped into the future for 20 years and he judges by his experience of 20 years ago.
Ashura and the others, in turn, have become much stronger in these 20 years, which is explicitly stated in the manga, and there is no reason to believe that they are not able to handle Enma.
The blacksmith kept these swords in his possession for the entire 20 years after Oden's execution, waiting for the appointed time. That is, the only person who has ever wielded these swords is Oden himself. During his life and after his death until the current events, it is not said or shown that anyone else tried to use these swords.
Ashura and the others, in turn, have become much stronger in these 20 years, which is explicitly stated in the manga, and there is no reason to believe that they are not able to handle Enma.
The blacksmith kept these swords in his possession for the entire 20 years after Oden's execution, waiting for the appointed time. That is, the only person who has ever wielded these swords is Oden himself. During his life and after his death until the current events, it is not said or shown that anyone else tried to use these swords.
Denjiro was holding two sword zoro easily. Others are all yc3/ close to yc3 level. What makes pre-enma zoro more impressive than them.