Regarding the lack of mods:
It could be that the game's rules change frequently enough to make it difficult to sustain and balance an overhaul mod. CK2, by contrast, doesn't change the rules that often, but usually extends the rules. That said, from the very beginning EU4 didn't have a great modding scene. Perhaps it's because the game works, and is improved regularly. Also, perhaps EU3 mods cast a bit of a long shadow, while with CK2 people could start "fresh".
Anyway, one thing I think the stats do show is that Paradox should add support for the Russian Language. If 5% of users (or is that 5% of mods?) are adding Russian language, imagine how many new users there are out there unwilling to mod the Russian language in?
Certainly for HoI4 they should add Russian language support.