Yugoslavia means (roughly) "Land of the Southern Slavs". It was intended as a union of all the South Slavic nations, which ultimately, weren't very dissimilar to each other on a cultural basis. For example, Croatian and Serbian, even though they are sometimes referred to as separate languages, are basically the same language, with perhaps dialectal differences.

Albanians, on the other hand, are not Slavs. Their language is pretty much unique from all other languages. They are also very different in other cultural areas: Albania has strongly entrenched tribal aspects, and a unique honour code, for example.

Basically, the Albanians aren't Slavic.