The Harvest Moon and Story of Seasons games were originally known as the Bokujou Monogatari series in Japan and developed by Marvelous Entertainment. Natsume held on to the name of Harvest Moon, while Marvelous continued work of Story of Seasons, making two separate series.
Both Natsume’s Harvest Moon and Marvelous’ Story of Seasons series started off simple enough: you were a city dweller in need of change, or you inherited a farm from a relative. You are then tasked to make the farm successful, make friends with the villagers, get married, and have a baby. After having a child, though, the game seems to get stale.
Marvelous and Natsume kept reusing the same formula, with only slight deviations in art styles and some mechanics between each game. The most recent installment, Story of Seasons: Trio of Towns, has brought new life to the series, but still lacks after-marriage content. Natsume has promised to bring back SNES era Harvest Moon gameplay in their upcoming title Harvest Moon: Light of Hope.
I do believe developers should have the freedom to create any game they want, and I would never make demands from them. But as a fan, I think there are a few ways both Marvelous and Natsume could refresh their respective farming simulator series.