Like many others, I play on and off (and the "off" periods can be months long) but always find myself returning to AC:NH. It's strange because in prior Animal Crossing games (Wild World, City Folk, New Leaf) I spent most of my time fishing, pestering my villagers, making designs, participating in events, etc... y'know,
playing Animal Crossing
. But in New Horizons, 90% of my time is spent terraforming and decorating.
It doesn't really feel like an Animal Crossing game to me because I rarely actually do the actions associated with playing a classic AC title. I can't remember the last time I caught a bug or fish in-game. (Pretty sure my net and fishing rod broke and I never bothered to fix 'em.) Every few months, I'm like, "Screw this, it's not even fun to play, there's nothing to do!" And then...
... and then I come back, because the decorating aspect, to me, is simultaneously challenging and soothing. I like working within the space constraints of my village, and going through trial and error to sculpt a town that feels true to me. I can't even count the number of times I've scrapped my terraforming and razed everything to the ground just to start over again. I hope this build will be the last time, because I'm genuinely loving the simplicity and open space.
So, long story short, terraforming and decorating keep me playing. I'm not one of those people who "finished" a meticulously decorated village four months in, because I'm a finicky perfectionist, so I'm still working on it. I tell myself that when I'm done, I'll be motivated to farm and fish and do errands for the villagers, but, heh, we'll see...