I want to know the answer to the following question:
Why aren't some sound clusters used in modern Czech?
All the background I'm provided with is that "It also contained a number of sound clusters which no longer exist; allowing ě (/jɛ/) after soft consonants, which has since shifted to e (/ɛ/), and allowing complex consonant clusters to be pronounced all at once rather than syllabically.". Is that enough to answer the question?
Answer: yes