my suggestion is to add a leveling system similar to oxygen not included where the hearthlings would get slight skill boost as they do tasks.
these 9 attributes would be increased by doing things related to what they effect so for example muscle would increase as they carry things around or do labor jobs. another example is compassion which could be effected either negatively or positively based on the hearthlings mood, so if they are unhappy for a long time compassion would decrease to a certain point.
I know this is kind of already a thing with the class perks but for general workers you could pre-train them for what job you want them to do.
you could also add a few other things that only generic workers can do, like gathering berries or finding and replacing things with upgraded versions.