Keep in mind that people are more vocal when they don't like something than when they do.
Absolutely this, ignore everything else.
It is completely standard that forums such as this one give an overly negative impression. Far fewer people post when they're happy than when they're not. It's commonplace for people to sign-up/delurk to post about some problem, or question, or complaint; far less frequent that they do so to post about how awesome stuff is. Though the latter does happen in this forum, and that's a good indication of how good the game is.
If you want some counter-balance to that, here's mine: EU4 is the best, most engaging, engrossing, complex and enjoyable game I've played in at least 20 years, and maybe ever. I now have more Steam hours (700) on it than any other game ever, nearly doubling the second highest. And that's over a period of under three months. I've made nearly 2000 posts about this game on this forum since October 13th. It has become my hobby, and indeed my passion (luckily I found it while on a sabbatical from work.)
Of course there are hundreds of things that could be improved in it. If anything, that's a testament to how good it is; there aren't many ways to improve poor products.
But regardless of that, the decision with EU4 is simple: Do you like strategy games? If so, it's almost guaranteed that you will be able to find 100 hours of fun gameplay from this game.
So the question is, is 100 hours worth the asking price? If you answer 'no' then, wow.. you have insanely high expectations. If, like any normal person, you answer 'yes', then there you go: buy the game.
Yes there may be things you dislike. Yes there may be features you think are crap; or major features you feel are missing. But the chances of that spoiling, or even hugely impacting your gameplay before 100 hours is pretty small.
It's a shame you didn't just buy EU4 a couple of days ago when it was $10, because then it was the no-brainer of all no-brainers. But at full price it is still almost guaranteed to be at the top end of return on investment for any strategy game fan, amongst all computer games you can buy today.
Although you missed all the Christmas/New Year sales, and the Humble deal, it'll probably be on sale again soon enough. The Conquest of Paradise expansion DLC is out and they're bound to discount it again before, during or after that time to encourage sales of the expansion.
But don't wait too long and forego the enjoyment. At $35 it's still vastly worth it.