As others, most notably Wiz have pointed out the "balancing around multiplayer" catchphrase is ludicrously overblown. At this point I'm beginning to automatically dismiss people that parrot this line ad nauseum.
I'd also dispute the idea that the EU franchise is being "dumbed down" or "streamlined," if anything EU4 suffers from being more complex than it's predecessors. AE over simple badboy, MP and branching ideas vs the simple tech and idea system, the new trade system, and the order of magnitude increase to the complexity of diplomatic relations. A good chunk of the complaints every patch stem from the unintended consequences whenever the devs tweak them.
EU4 isn't perfect, but as others have said it's still overall an improvement over what came before. The big problems with it right now are the underwhelming DLC and poor maintenance of them (The American Dream is still broken from CoP with no plans to fix it, which is simply reprehensible), and the way balance jumps around each patch. For example, aside from AE jumping around, the rebels in 1.6 were practically the same as the rebels in the version at release which had previously been patched out.
The only major design decision in EU4 which I dislike in theory and in implementation are how Monarch Points are used for tech. Others again have pointed out their particular faults much better than I could, but overall I dislike it compared to EU3's tech system as it changes technological advancement from a system that depended mainly on the strength of your country's economy to something that you advanced from the "top down" with a simple click of a button. I would actually prefer to see technology advance more organically with less direct player control than it does now, i.e. rather than directly advancing technology, the player should create conditions in the nation which then lead to technological advancement.
Which parts of American Dream are still broken? I thought we fixed the issues with TC->USA not firing the events in 1.7?