Most people commenting in this thread have quite a bit of DLC under their belt, recurrently with CoC drilling & disbanding as a point of discussion, i don't usually see a lot of debt in my lowish DLC games, though i have never seen the AI go bankrupt since the new economy AI behaviour went live. Probably becuase bankrupted AI's being forced into truces with those around them isn't very fun at all.
Also ill add, in the cases where they do accrue debt, countries like France (a particular example) will refuse to pay loans unless immediately joining a war based mostly on trust and diplorep when i've gifted them the amount directly (yes i know you can remotely pay credit with RoM) which is a annoying block to them joining a war whimsically. And they often simply buy their entire manpower tool, this works up until they suffer one or two bad losses which hurts their army composition significantly.
Considering psychology, maybe they should
re-tool the AI personalities system especially since it is a crutch of what they're doing and its had no polish since forever, and restrict the super aggressive infrastructure building to a
'economist' personality ruler, since diplomat seems to be well rounded, while militarist and balanced technically do what are asked of them.
Administrator is supposed to be what ive just suggested, but it never lives up to the hype and should probably be refocused somewhere else like a AI type that actively seeks to assert control over its own territories so will more than likely hit autonomy buttons & liberty desire reductions in order to maintain on top of the situation rather than delegate this entirely to economy.