It's the same shit with MADS. Yes, it's lame Oda didn't explain it more, but when Vegapunk hasn't been revealed yet, it's understandable why we haven't gotten elaboration on it.
Same with King and his species and why they went extinct.
Same with Kaido and his species potentially (Oda still hasn't addressed what Oni are).
Same with Rocks plot
Same with "the dawn" or Zunisha's role
These are just things he clearly wanted to tease and not actually answer. It's an ass justification, but I'm sure we'll get explanations in the endgame. A lot of this doesn't just leave the plot. Rocks stuff is still relevant post Wano with Blackbeard/Shanks clearly.