What can be done about abysmal AI decisions for Singleplayer/Achievements?

I feel like singleplayer campaigns have become increasingly unplayable due to the absolutely horrible AI. I remember a time when the AI declaring wars on random countries or spamming 6 widths and winning by attrition in 1960 was the lesser evil compared to what we have now.

Italy used to at least struggle for a while in North Africa, now they just get steamrolled instantly. Germany got a reworked war economy mechanic that the AI can't deal with and the only reason they sometimes win barbarossa is because the Soviet AI puts half the red army on Iran or the Japanese invasion, because apparently losing all you land equipment to China and all your ships to the US makes the Japanese AI think now's the time to mess with Russia.

I get you're supposed to help out your allies as much as possible and that there are AI mods - but what can be done for achievement runs?

I just wanted the Hungary achievement where you need all your historical cores and proclaim Greater Hungary, but not even that seems possible if Germany declines Slovakia and Burgenland in a historical run (!!!).

I'm not playing the same game over and over and put days into this just in order to figure out what buttons to push with some moody miracle AI to receive what should have been Hungarian territory in every single historical campaign.

I mean it's not worth my time if the very basic mechanics work against the player and I must do half a world conquest every single time or else everything turns into a lagging war of attrition.