Victoria II, without mods, can be fun, but it get stale very quickly, it realy lacks content, as most Paradox games do;

The army management isn't bad in early game, but mid and especially late game, it turns into a chore; it lacks QoL, such as army templates and not having to manually manage the battalions losses;

There's barely any content in the game, after playing it in vanilla, after 3-5 runs you will feel that the game is empty, there are barely any political decisions to do, even as a relevant nations like Austria;

The economy is a bit of a mess, I doubt that even the devs know excatly how it works;

Spheres of Influence are a neat mechanic, but it also needs QoL, mantaining a sphere of influence with many countries is boring, early game Austria/Prussia, if you plan to create Germany, is annoying as hell, it should have at least some degree of automation;

The research tree is good, the combat is also fun, the way that cultures work is also great, but religions should be a bit more important in the game;

But still, this is my favorite Paradox game, with mods it really is a blast.