Kyros took out Diamante (which is the much more appropriate comparison).
If Jack was to be defeated by a Strawhat because the Strawhats need to surpass the Beast Pirates, I would have expected Jimbe to face him (Fishman vs Fishman, water abilities vs "The Drought", etc.).
If Jack's opponent is not dictated by such concerns but by narrative, well Inuarashi as a much stronger case than Yamato:
Inuarashi is the one who has an extensive grudge and narrative build-up for his conflict with Jack:
- Jack attacked his country
- He fought Jack for 5 Days with Nekomamushi
- Jack laid waste to his country and his people with poison gas
- Jack tortured him
- He lost one of his legs to Jack's torture
- Together with Nekomamushi, he defeated Jack in Sulong.
- Jack sought the Dukes and Raizo out to finish things with them.
- He specifically prevented Black Maria from going after the Scabbards so that he could deal with them himself
- He defeated several Mink soldiers to get to them.
- Inuarashi stayed behind to stop Jack and prevent new victims:
My God, the amount of narrative build up for Jack to be defeated at the hands of one of the Dukes is something else. And people want Oda to throw all of that away? For a fight that has zero setup? Because their headcanons do not agree with what the narrative suggests?
There has been no on panel relationship or conflict between Yamato and Jack. Why then should Oda abandon Inuarashi's narrative for that farce of a matchup?
Frankly I think it's terrible writing to discard the narrative of Jack vs the Sulong Dukes to satisfy some notion that the Beast Pirates must be bested by the Strawhats. It would be a disservice to Inuarashi's character, the Zou arc, and the entire Mokomo Dukedom.
If Oda wanted to go that route, he didn't need to repeatedly reinforce Jack's conflict with the Mink tribe in all his on panel appearances in Wano.