Minus Kanto, the three regions based off of Japanese regions I think relied heavily on lore in their designs. With exception of Hoenn, when people think of the regions, they're not really thinking of the land structure itself but of what its themes stood for. It almost kinda seems like they wrote a region around these concepts of myths and tales of creation since the legend of that generation acts as the heart of the region that keeps it together. (Ecruteak, or at least the general area that includes Violet City and Ruins of Alph is Johto's heart, Sootopolis is Hoenn's heart, and Mt. Coronet is literally the centerpiece of Sinnoh.)
For Unova, what can you say would be its heart? Probably Dragonspiral Tower... and that's it? Relic Castle may have the region's lore, but nothing really significant occurs there unlike Dragonspiral Tower. N's Castle is important although its lore is scant due to being more modern in comparison to the ancient tower, which could help contribute in the theme of the conflicts of truth and idealism especially since the landmarks are literally on the opposite ends of the map.
Kalos has the lore of AZ and his ultimate weapon that nearly destroyed the region, but was his kingdom originally located in Geosenge Town where the weapon is being held? We weren't ever told about it, were we? The heart of Kalos might be Lumiose City since it's the largest city in the region and is literally smack-dab in the middle, but... nothing significant happens there outside of it hosting Team Flare's hideout. Terminus Cave where Zygarde sleeps may be the actual heart of the region, but it's so neglected both in-game and meta. Why was Zygarde situated there in the first place if it's just a coal mine? What makes it so special?
Alola has the guardian deities on each island in which each island has its own little history, and in Vast Poni Canyon lies the Altar of the Sunne/Moone, that's how you get to summon Lunala or Solgaleo depending on the version. Perhaps that's the heart of the region--but nah, let's not focus on that, we gotta restore the balance of the Pokémon world by entering the Ultra Beasts' dimension.
Galar has... uh... actually I don't know since I haven't been keeping up with the region. Like far as I know, there may be two areas of significance, one that's in the main game that I guess is near your hometown(?), and the other is the Crown Tundra further up north. Though I guess the heart of the region is Eternatus itself which sleeps underneath Hammerlocke, which is I think the oldest city in the region just from some quick searching. And it's technically in the center of the linear region.
But otherwise... I couldn't tell you the lore of the regions past Unova (and that's barely). I don't know if Game Freak approached the later regions the same way as with the Japanese-inspired regions, but could've fooled me otherwise since it feels like they were taking the backseat compared to Johto, Hoenn and Sinnoh.