Yes, you are pushing an agenda. Most of your post are you pushing an agenda.
There's no blacksmith speculation. Blacksmith creates swords so the quality is determined by them. It's that simple.
Ace is a higher grade than Shusui but not a superior sword. Ace can't break Shusui but Shusui can break Ace. A superior sword wouldn't break against an inferior sword. Once shusui became a black blade it became superior to all normal blades. The only swords superior to shusui are supreme grade black blades.
Swords that are at least a decent quality don't easily break. Effort has to be put to break the swords. Zoro used Kitetsu III (fine grade blade) to block Shusui (excellent grade black blade) and it didn't break.
Zombie Ryuma had to use a sword breaking technique to try to break Zoro's inferior swords and they didn't break because Zoro countered Ryuma's attack before he could break them.
My reality is backed by manga facts.
If Wado is as durable as a black blade then there is no purpose to black blades. Your reality makes no sense and goes against the manga.