Let's try applying your idea of the perception of the Hebrew writers to
the perception of English writers. How would you explain the perception
of English writers and the written inventory of 5 basic symbols for the
vowels (a, e, i, o, u)? Are you saying English speakers only really
perceived 5 different vowels? Maybe we can even extend that to the
consonants? English speakers generally only use 21 consonants? Could we
then say English speakers really only perceived 21 consonants? If we
throw in the digraphs (such as th, sh, ch, gh), what then? And, would
you say each of those only have one perceived phonemic value?
Just as a side note, when I was a child, long before I knew anything
about consonant only alphabets, I would occasionally write notes to
myself dropping all the vowels (this was something I had come to on my
own, it wasn't taught to me, it just seemed quicker to write it that
way). While it is not to difficult to read a English sentence written
this way, it is easier to do so with semitic languages. If you can't
seem to understand how the semitic root system plays such a large role
in making writing without vowels so much easier (as others have previous
tried pointing out) then I would not know where to begin to explain that
to you (it should be almost self-explanatory to you if you understand
any semitic language).