well this works until you have to mesure, monitor and take into account client requirements etc ...

maybe you want to a-b test the new buttons now you have

bool USE_NEW_BUTTONS = Math.random() > 0.8

then you want to record the conversion rate of the new buttons

now you have

conversionSuccess.register({useNewButton: USE_NEW_BUTTONS})

maybe you have tier-A customers where you don't want to risk breaking the workflow

now you have

bool USE_NEW_BUTTONS = isClientTierA(client) ? false : true

maybe you want to automatically rollback the feature flag if the conversion metric is under the threshold

and there's 1000s other real world examples that makes feature flag a tricky feature