There's a bunch of counter-argument here from working practising blind mathematicians who read and write raw TeX every day, so there's at least a non-zero audience.
There were a bunch of mathematicians who used roman numerals for arithmetic between 0 AD and 1200AD. That they existed is not a counter-argument to the fact roman numerals are terrible to do arithmetic in. That is an argument that people can get used to anything, and become proficient enough at it that changing to a new - and better - system will set them back enough for it to be not worth while doing - for them. The same is true for modern maths notation.