Crafting! I love crafting things into other things, trying to get as much things to craft them into something else, selling my crafts and gifting them... I like all parts of the game that lead to a crafting outcome, so farming, mining, planting and chopping up forests, etc.
I'm not so fond of things that can't really be crafted into anything meaningful or profitable, like fish - I mean what's the use of them, other than to put in the fishpond for farming roe? I wish there were some more profitable / useful fish recipes. Although I'm currently slightly obsessed with catching sea cucumbers and making them into lucky meals - this is great!
Also, I'm sure this is going to be a very unpopular opinion, I absolutely love TRASH. There is something absolutely, wonderfully wholesome about being able to clean up the environment, pick up all the trash, and craft it into useful things like cloth, iron, coal, stone, crystal etc. I definitely wish there were more recycling options. Mr. Qi could provide some super-recycler blueprints to turn all those artifacts into strange and amazing things like radioactive ore and hyper-gro.