>>44257972I mean Gen I didn't have a gimmick, Gen II yeah, Gen III arguable since Hoenn introduced a lot of environments not seen in the series yet and went pretty hard into them. Gen IV is arguable since Gen II had done Pokemon Evolution as well and Gen III had done Form Changes, I guess if you wanna call them Gen IV's thing then sure but it's hardly unique to Sinnoh.
The Origin of Pokemon could arguably be tied to the three Dragons although Unova doesn't really have a central gimmick, yeah there are one-offs like Triple/Rotation Battles, Seasons, etc. but none of them are as omnipresent. Gen VI is definitely on the gimmick side of things. Gen VII's a bit weird, to my knowledge Kukui doesn't actually bring up Z-Moves that often throughout the game and it seems to more so be moves in general, he is at least tangentially related to his region's gimmick.
Magnolia definitely falls under the gimmick umbrella although given how fuck all we see of her (or anyone who isn't Hop or Sonia) in SwSh they don't really play into it as much as the previous two. Sonia doesn't play into her region's gimmick since History is hardly a unique element to Galar, hell Hoenn got retconned to have the history of the Weather Trio be made more important.