Yes, communist ones. Now ask yourself what system is better, the one growing at a 5% GDP and average income yearly, or the one stagnating and turning to fascism

no of course not, but the breakup of Yugoslavia is a special case...

Although you could argue that the SFRY in (especially late) 80s was hardly socialist anymore, since they had to implement exceedingly more wide-reaching reforms dictated by the IMF. Thus giving rise to material conditions which could be exploited by fascists as soon as the strong suppression of fascism stopped (which started much sooner relative to other ex-socialist countries, thanks to said reforms).

Or even that it had stopped being socialist with the beginning of deeper implementations of "self-managment socialism" (to judge that is out of the scope of this comment), giving more time for those sentiments to foster.

Ofc the sudden rise of fascist and (ultra-)nationalist forces wasn't only bc of material reasons, even if they fed the spread of it. Culture, questions of ethnicity and nationalism played a huge role for both historical and structural reasons.

Yugoslavia was a multi-ethnic state with deep interwoven ties between it's peoples. A part (or result or reason for, again out of scope) of that was either a confused dispersion, or deep regional integration of said ethnicities, depending on how you put it.

Here is a map based on the 1981 census

To cut things short, ethnic tension was one of the main problems the '74 constitution tried to solve. It didn't succeeded, but was able to prolong it's "explosion" for quite a while.

With the gradual weakining of the central government – aggrevated by Tito's death – nationalism was allowed to spread or even cultivated inside of the individual republics...

Edit: another thing (aside from western intervention ofc) that enabled the dream of unity and brotherhood between the southern slavs to turn into a nightmare:

It's the military doctrine of "Total Defence"

The JNA adopted the concept of total defence (as did a number of other small European and neutral countries). Yugoslavia based its defence doctrine upon the total war concept of "Total People's Defence" (sh. Opštenarodna odbrana / Općenarodna obrana) which drew upon Yugoslavia's successful partisan history during the Yugoslav People's Liberation War during the Second World War. "TND prepared the entire population to contest the occupation of the country and finally to liberate it. The Territorial Defence Forces would mobilize the population for this purpose. The combat readiness of the TDF meant that the steps of organization and training could be bypassed after the start of hostilities. The TDF would supplement the YPA, giving it greater defensive depth and an armed local population ready to support combat actions." The entire Yugoslav population was to be engaged in armed resistance, armaments production, and civil defence under this concept. It was believed by the Yugoslav planners to be the best method by which a smaller nation could properly defend itself against a much stronger invader, specifically, NATO or the Warsaw Pact.

• https://en.wikipedia.org/wiki/Yugoslav_People%27s_Army#Doctrine

also:

• https://en.wikipedia.org/wiki/Total_defence
• https://en.m.wikipedia.org/wiki/Territorial_Defense_(Yugoslavia)

yet another reason was the liberlization of religious policies which led to more freedom for the catholic church and of muslim organizations, which fostered nationalistic oppition in both Croatia and Bosnia

(those are the instances I know of, might be that religious orgs of other beliefs did the same and/or additionaly in the other republic)

Edit1: writing this comment made me wanna rewatch the following video: History of Yugoslavia through music ♪♫.
It always manages to make me tear up, especially "Samo da rata ne bude" at 12:30 which practically devestates me. every. fucking. time. after that still but less so

Here is the full version with eng translation: "Samo da rata ne bude" - Yugoslav Anti-War Song [Just let there be no war]

Edit2: in it of itself "Total Defence" is a sound doctrine and the SFRY executed it quite well with their own characteristics. It's not inherently bad, I do not mean to critize it, just inform about some ground laying aspects of the following wars; their unfortunate and partially coincidental combination just lead to horrible outcomes