Simple solution - Introduce Hay Day Solo
It would be so easy for Supercell to address this issue - simply spin off Hay Day into Hay Day Solo - the exact same game without neighborhoods or the Derby. They could either allow you to migrate your current farm or make you start from scratch. Either way, everyone goes home happy. You could even have it both ways by keeping your current farm in the current game and starting a new one in the solo game.
(Then they could spin off Hay Day Solo - Derby version, adding a single player Derby version. Now they have three games churning out revenue in place of one.)
Otherwise, one of the other farming games is going to clone the original (there are close imitations now) and suck up all the players who remember how peaceful it used to be.