Why is it that when looking at the culture of Europe today, Romance language and culture has survived further inland in now Romania, but not in former Yugoslavia?
As far west as Iberia saw widespread Roman settlement, and Roman influence created a culture that lasts to this day, but just across the Adriatic from Italy they still speak South Slavic.
What about Roman Illyricum was different than that of Rome's western provinces so that Slavic, and Albanian culture survived there?
I'm not totally sure what you're asking about. Illyricum was plenty Romanized. Quite a few of the later emperors were Illyrians, most notably Diocletian. Slavic languages are spoken in the area now not because they survived Romanization but because they replaced Latin and the native languages--Slavic is a relatively new arrival to the area, only appearing during late antiquity