Yugoslavia's ethnic tensions only happened as a result of its financial problems. The economy was dependent on IMF loans, Yugoslavia wouldn't even be able to pay the principal amount, let alone the interest by the '80s.
Hyperinflation and unemployment above 10% during the '80s, even with 1/5 of the workforce living in other countries as foreign workers, discredited the political system and radicalized the populace towards nationalists on both sides. The central government lost fiscal control over the republics, and politics devolved into national arguments about who "stole" from who.
The Economy of Tito's Yugoslavia: Delaying the Inevitable Collapse addresses Yugoslavia's postwar economic history very well.
Yugoslavia would've needed a capitalist market economy to survive. Pre-war the King was about to give the Croats and Slovenes autonomous Banovinas, a similar framework could've worked postwar.
Yugoslavia is probably the only nation that would have benefited from being in the axis during WW2. Without the 1941 coup, Yugoslavia been an axis minor to provide natural resources for the German war machine, or minor troop contributions as with Hungary and Slovakia. German influence on Italy and the axis minors would prevent a total partition of an alt-Axis Yugoslavia as in OTL, and the Kingdom would suffer at most at third Vienna award that leaves the Serbo-Croatian core intact (preventing Jasenovac, the NDH, and the bulk of the civil war).
Yugoslavia may even have been neutral on the eastern front as Bulgaria was, or pulled an Italy and switched sides once the writing was on the wall.
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