I think the ui migh be one of the main problem, i don't think it is bad but it doesn't seem very good either. When streamers of their studio have trouble finding the right button it should raises some questions. Of course, streamers havn't developped the wole game and are not always programmers but a good ui is a ui you can undesrstand easily, especially if they intend to find new players with no experience in their games. In complex game like I:R it is difficult to make good ui, but some icons seems to be not that clear what they are(they always click on 3 buttons before finding the right one between diplomacy/religious .etc tab, same concern for tactics and quite subjective "attributes" for animals"). For example the agressive expansion icon, i might be the only one to have the issue but i think there is not enough contrast between the sword and the paper, I had to take some seconds to figure out what was this icon. Some of their programmer even mentioned on the dev clash it was not intuitive to find the war exhaustion (because it is in religion tab not war tab).
Ledeger was good but maybe a bit cheaty, in eu4 I use it to check exaclty how much troops my ennemies have before delcaring war. It would be best to have a spy system. You have to send spy/bribe high ranked officials in foreign countries to estimates how much troops they have, what is their economical and political situation, who has a low loyalty and might defect to you... Trade could be used to reduce spying cost/increase success chances, this way you will have to think twice before agreeing to trade with someone else (If AI take it into account).