This is just my own opinion, but I know quite a few other people on the forums share it. So here ya go:
Allowing players/AI to develop provinces was bad for the game long-term, in my view. Base tax/production/manpower was meant to abstract EU3 population and resource mechanics in an easy to understand way. Province base tax/prod/manpower were largely static over the course of the game, only changing with major events. Pre-CS EU4 development essentially worked like EU3; while the EU4 world's population would no longer increase over time as it did in EU3, the relative strength of highly populated and sparsely populated regions largely remained. The early development system for EU4 worked quite well, all things considered, and tended to produce historical outcomes. Some regions had lower development and were more challenging than others, but that diversity was part of the fun.
With this in mind, the development mechanics introduced in Common Sense flattened the landscape, so to speak. Developing provinces is the equivalent of materializing population out of thin air using monarch points, resulting in silly, ahistorical outcomes where Ryuku can acquire the population and production power of Paris or Beijing within a couple generations, when in the past it used to be a tough challenge for Ryuku to field more than 1-2 regiments. This becomes especially strange when you take into account how monarch power interacts with the number of provinces and tags in the world: more tags = more monarch power, which means absurd levels of development in certain regions of the world.
As someone who originally fell in love with the EU series as a historical simulator, it pains me to see one of my favourite games transform into a 4X. I was optimistic at the time Common Sense was released, but after observing how it affected the game's direction I've come to the conclusion that it changed the game for the worse.
