Short answer: Every language has distinctive consonant clusters. Glosa has inherited its from Latin and Greek. Many other languages have inherited them too.
If there is one thing I can add to the textbooks to make the pronunciation simpler:
One thing that irks me at Christmas time is when I hear the Latin GLORIA IN EXCELSIS DEO, and the choir pronounces EXCELSIS “eks-tchel-sees.” It should be pronounced “ek-shel-sees.” The S-sound from the X combines with the soft C to produce the SH-sound.
Glosa follows the pronunciation rules of Italian and Church Latin. They don't go for such difficult consonant clusters. I think this will make the following words a little easier to pronounce:
I also pronounce PLUS-CO “ploo-shoh,” EX CIVITA “ek-shee-vee-tah,” etc.