Honestly, it's usually events here on The Bell Tree Forums that gets me back into the game if I haven't played in a while.
My island was pretty set for a few years, but I've been thinking about doing some major terraforming to make a few things look better. Not exactly enticing incentive to return to the game, since it will be a lot of work, but it's a long term goal and something to look forward to.
I also got a second Switch and another copy of the game last year so I could make a second island because I came up with a cool concept for the island and have villagers I want to experience. I've yet to create that island, though, because I need to come up with a name for the island. That gives me some motivation too, albeit of a different sort.
If you keep playing New Leaf and one of your villagers pings and requests to move, decline their request and then save and quit. You can then safely time travel ahead as far as you want and no one will move out. I've done this before to repair grass erosion in my towns.
Sometimes when you tell villagers not to move out, they'll still stick with their plan to move out anyway, so you should save before doing this just to be safe. Reload without saving and then try again. Once they agree to stay, you can safely save, quit, and time travel to whatever date you want and everyone will remain in your town. You'll just have to deal with weeds if you don't have the Beautiful Town Ordinance, kill the cockroaches in your home(s) and go see Harriet to give you a haircut to remedy your bedhead.