Maybe this is an old issue that is already decided upon, but aside from the actual game mechanics of monsters razing cities and making the ground infertile, I think that the storyline needs to be fit in a bit better to the mechanics.

For example, the game is supposed to start after a massive cataclysm. I assume that many of the monsters that virtually destroyed the world are still hanging around, being those death demons and shrill lords and such. If so, it makes sense that these monsters would still be razing what they could.

However, if this is so, they should be razing land wherever they go, and not only when they raze cities. Furthermore, these razing monsters should be surrounded by infertile terrain, and fertile terrain should only have in them monsters which do not infertilize as part of their razing process. Also, there could be theatrical/storytelling reveals for defeating the various monsters and cleaning out their lairs. Stuff like maybe that river slag that you had to kill before founding a city in a nice area used to be worshipped by some unknown civiliation in history as a friendly deity (as evidenced by drawings and carvings on rocks by it's lair) before the cataclysm in which it went mad.

Working on game mechanics to make sure things are mechanically fun is valuable, but especially this being a solo-player game, the in-game storytelling really should match the mechanics, and there should be a lot of storytelling. (Perhaps with an option to ignore certain story elements which are not essential to gameplay for certain types of players.) It will make the game much more immersive.