A cake recipe is not a cup of tea where you can remove sugar without changing much else. Sugar contributes to the way many batters hold moisture and set, and to how cookies spread and color.
If you want a less sweet dessert, start with a recipe designed that way or choose fruit with a modest topping. Removing a large fraction from an unfamiliar recipe may create a dry or unusually shaped result.
For experiments, make a small batch and record the change. Taste after the bake has cooled enough for its intended texture to develop. A warm bite does not always reveal how it will eat later.
Liquid sweeteners also bring water and their own flavors. Maple syrup is not automatically a weight-for-weight replacement for granulated sugar. Use a formula that accounts for those differences when the bake depends on accurate proportions.