Assuming that what I’ve read (extremely quick search) is true, too much sugar can cause diabetes and heart disease. So reducing the amount consumed will likely improve public health. It’s not a big jump from one to the other.

Also, in the article I first linked there’s this quote: “These seemingly average changes can lead to valuable changes in health at the population level” by Dr Oliver Mytton (UCL Great Ormond Street Institute of Child Health).

So yes, there’s been a positive impact.