You know what I don't like in EU4 achievements?
Many of them are assigned to typical 'boring major power 1444 historical nations': Spain, Portugal, France, England, Muscovy, Ottomans - while I have nothing against Super Difficult Achievements (like FORM PERSIA AS 2 PROVINCE TABARESTAN

) I really don't like
tedious achivements and requiring you to spend 30h*6 nations to get 6 achievements - without guarantee you will get them as this is Ironman - is a bit brutal for completionists like me 
. The same is for Civilization 5 which has 43 nations and there is one achievement for winning as every one of them.
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I also think achievements relying on pure luck are simply pointless and annoying>
Still, in Civ5 I have 77% of achievements because a lot of them encourage diversified gameplay or doing cool stuff + they aren't as restrictive as EU4 ones - I don't think I will have more than 17% in EU4 as
unability to get achievements without Ironman makes normal games more fun for me, not to mention mods.
I am not going to play as particular country for 30 hours - without mods, with lucky nations I dislike as they limite unpredictability, without regular fun coming from console 'fog of war and terra incognita off and look what's happening in the world' and my favourit settings - just to get one very particular steam icon.
Personally I would design more:
- achievements which require doing something cool without restriction of one particular nation
- achievements for specific areas of the world, encouraging trying ROTW 
- easter egg or pure fun achievements instead of X variations of 'conquer everything on your way as nation Y to get achievement icon Z'
etc.