Same for me, and it is quite bizarre. In my case, betas worked just fine, I mean they even seemed to be performing better than the previous solid built. I got the Choson One achievement and played until 1780s with the first beta and it was all fine. Then the update came properly and now the game becomes REALLY slow after 1550s... Which kinda makes going for longer achievements a chore, not fun. I do not know, perhaps it is an illusion. Stellaris' latest update dropped around the same time period, and it features EXCEPTIONAL performance improvements. It is not only a joy to play it now, but outright a blissful experience even on my 6 year old Macbook Pro.
Moral of the story: I am no computer engineer but the performance of EU4 is not getting any better lately. This is quite sad seeing that the team is coming up with wonderful new additions to the game for us, flavor that I enjoy so very much. If only we had a dedicated team like the Custodians for Stellaris, that helped EU4 perform better I think the player base in Steam would skyrocket once again. Performance really can make or break any experience, and in this case I will sadly seem to have to wait for its improvement before heading on to try my hand at another 50-60 planned achievement-oriented campaigns. Stellaris campaigns should keep me busy in the mean time.
