Ace is still relevant at this point in the story.
I won't surprised if a inhabitant of Laugh-tale says "You remind me of Ace" upon seeing Luffy.
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Seems like Rocks Pirates "Only defeat" is the God Valley Incident.
That means did you want to say if "Apprentice Kaido" get low diffs by Garp and Roger?
Not really. Kaido could have lost to some other pirate before he was part of the rocks and big mom might have saved his life.
Even if he was a part of the rocks, some pirate might have challenged kaido alone and won. The rocks pirates don't give a shit about their crewmates , so big mom might have been the only one who went and saved him.