I think even if it changes, the reward is still too small because others can build there also.
The effort I spend on killing a boss monster, I usually could steamroll the rest of the AIs combined instead, it's a diversion/challenge mode instead of a part of the regular game.
I agree with this. Not all of the wildlands are ridiculous, but most of them I simply avoid.
The Caverns wildlands is great because it takes time and has some significant risk (the last cave is murder). You can theoretically access its benefits from turn one, but it takes a late game stack to finish it off.
The Ruins of the Empire is tough to get into, but is worth it because of the really tasty shards and resources in there. Plus, once you fight the obsidian golems off, its a matter of cleanup. Again, its a mid game access to an extremely nice city spot.
Scrapyard can be worthwhile if you have a lot of units which avoid armor, but the amount of time and effort it takes to get there if you are not focusing on magic makes it worth simply ignoring.
Anything with an actual boss is realistically only going to get completed if the player feels like taking a break from grinding all opponents to dust. By the time you can beat them, the game has already been long over.
I think there really ought to only be one of the really truly brutal wildlands, one or two of the midgame ones (scrapyard/ruins), and one or two that you can tackle if you focus on them early-mid game with the reward being a really nice place to put a city or an extremely nice place for an outpost.
