There is a lot of issues at work here, at a fundamental level, with how Paradox handled their expansions (DLC).
In the past, before the advent of DLC, adding new features was done solely through paid expansions. You would have to buy the expansion to get any of the new features and additions, otherwise, you received nothing, except maybe a bug fix/compatibility patch. Lots of games still go this route, when it comes to major changes, and offer smaller, bite sized additions as DLC.
Paradox handles expansions differently now, largely as a token of goodwill to the playerbase. Someone who has only purchased the core game can continue to receive lots of free additions that expand the game in new ways, without having to ever pay Paradox again. Very few companies do this outside of MMOs, or developers who really bungled their game and want to fix major issues. By and large, this is a very good thing Paradox does, otherwise we would all have to buy every expansion to get anything that the vanilla game doesn't offer.
Lots of people complain about this, though, and see it as a paywall, which I don't quite get, since these people are receiving free stuff and frequent updates, just not all of the DLC (or Paradox will not ever make any money). I'm not entirely sure where the sentiment comes from, but that's just my lack of understanding, I guess. But I can see where this chafes people, since there's a bunch of buttons they can't click.
From what I can tell, the baseline development of the world is a lot similar to what it was before Common Sense. So really, not being able to develop your provinces doesn't change a lot if you don't have the DLC. I am not sure if the AI is allowed to do so or not, but if it does, then you can just conquer their land (or acquire vassals) as a work-around to development.
While it would be great if all of the expansions were free, Paradox does need a flow of income to continue to improve and expand EU4. DLCs are by and large cheaper than the expansions of the past, which tended to fall around the $30+ range, and offer less, and there were no free content patches, either.