That's not really true though. Take the IPA 'j', that has the sound of a
'y' at the beginning of words in English, like 'young'. Obviously I
picked an easy one that you can represent with the normal Latin
alphabet. But you basically go "this character here means what we call a
lateral spirant, which is this noise", in case anybody's wondering
that's the so-called double-l in Welsh, among other languages, e.g.
Navajo. So yes, it was developed by sighted people. But there's nothing
particularly sighted about it. I could just say 'cdj' represents the
final sound in the English word 'edge'. Put another way, everybody has
to learn it. There's nothing about sight that makes you look at an 's'
with a mark under it and immediately go "ah yes, that's the 'sh' sound,
as in English 'ship"! You learn that when you learn the IPA. Now, maybe
it's harder because nobody bothered to name the IPA characters. But
assuming for the moment that they all have some sort of name attached to
them, all you need to know is that currently unannounced character foo
means noise bar, and of course you need character foo to be announced as
character foo.