by 10% you mean 10 players?
I see EU4 vets like Fin and Zlisch play EU1, there are others I'm sure.
Me, Fin, Hate_More, and XyNox are the only more or less dedicated EU_4 players who play on EU_1, all of us (tbh never talked to XyNox that much) dislike EU_1 and play way less on it than we used to. Half of Fins clan, several clanless people, and every GoatsPriest besides me, have stopped playing though. Besides Fin, do you even want us on EU_1?