I think giving the option to skip it is a great idea! I do get the fun of filling the map in an aesthetically pleasing manner, but since you're only given set options to do so it ended up feeling (for me) more like a chore than expression, like being forced to put a mountain / forest / river *somewhere* instead of where I would have liked to put one in a more visual sense.
Maybe a nice middle ground would be to have the skip option and make it quickly autofill the map before ending the level, similar to how the humans build on their turn, so that all players can have the satisfaction of seeing the remaining spaces covered by nature?