Public folders for legacy users were supported for several years after new users stopped getting the feature. The actual number of people still accessing public links after those years was quite low...
But yea, it certainly sucks to have to remove functionality, especially from such long time and loyal users. I just want to make the argument that this wasn't done to somehow trick people into upgrading their plans, but with the goal of creating a better product (which sometimes means a simpler product).
edit: For a timeline breakdown...accounts created after late 2012 stopped getting public folders. Public folders for legacy users kept working until March of this year. That's ~4.5 years of support for a feature only accessible to legacy accounts. They certainly did not foresee Dropbox Professional when they made the decision to stop creating more public folders. https://www.dropbox.com/help/files-folders/public-folder