I'd just like to point out that for a paid product like Leviathan, the 'complexity of the release', in principle, and ignoring the human aspect of all development things related, shouldn't matter.
When a construction company is contracted to build a bridge, it is fair to expect it to build one in a way where it doesn't immediately fall apart when a large truck tries to pass it
When a football player is selected to represent a country in a World Cup team, it's fair to expect them to not immediately score an own goal
it is completely normal when certain people, companies or entities are held to certain standards, and that people are disappointed if those standards aren't met, even if they wouldn't be able to do it better themselves.
There have been a lot of extreme, toxic, voices surrounding Leviathan's release(as is the case with.. anything) but I firmly believe that in general the backlash against Paradox was justified.
And to maybe reiterate; just because of how complex developing a game like EU4 is, it's very much natural that there are little parts of the development process that certain members of the community likely could've done better, even if it's unlikely that they could perform much better as a developer "overall".