Where do you want me to start? FJ was a reactionary who presided over a ramshackle 'Empire' composed of lots of people who hated each other. The KuK was led by a paranoid functional incompetent who panicked at the wrong moment in 1914 and redeployed an army that should have been sent against the Serbs. After that it was all downhill, including the siege of Przemyśl, which was an utter disaster. When you have umpteen languages for your officer corps to try and learn so that your soldiers can understand you, you have a problem.
Okay, i start here and as for today, i probably end it too, maybe tomorrow... errr, today later i continue.
FJ was at least medicore, but public opinion about him.. well, Ferdinand was believed more intelligent. Much more.
The Przemysl fiasco was a clear sign of the utter retardation of the higher command - not so long ago i was fortunate to run into a quite good piece about the sieges, and man... faceplam time.
However, language: not a big problem. At all.
The austrian side of the army trained in and teached german (hungarian side ofc hungarian and... german). The men spoke some horrible military-german (like my great-grandfather) or even almost regular german - long story short, the officers and the men understood each other, just cannot enter into a conversation about astrophisics. Or they can, since the officer corps - reserve included - spoke languages, local languages and the units raised regionally, again, including the reserve officers.
Of course, personnel could and indeed have made some erratic decisions, hungarian officer speaking french, german and some slovak commanding bosniak jaegers, but... he could commanded in german, and after a few months, he ruled the language enough for small talks and so.
Was it perfect? Nope. But it worked out, even after the enormous losses in officers.