As someone who is a Paradox fan, is now working at Paradox, and currently able to play EU5 freely. I personally disagree.
Same as with any game in development, there are a plethora of things that require polish, tweaking, fixing, etc.
Is the game "Playable"? Yes, like Johan has said it's technically been "playable" for a long while. But playable =/= ready for release. I suspect many would ask us "Why would you release it in such a state" if we decided to release it on a whim, rightfully so.
Do I expect a perfect release? No, there's always things we don't catch or things that require more tweaks. With a game as complex and content filled as EUV that applies even more so. I believe a "Release when we are ready" policy works a lot better regardless.