What LaTeX replaced was: a) typing the text of math papers and writing in the formulae by hand. b) word processing which was fixed width and line based, where

What LaTeX replaced was: a) typing the text of math papers and writing in the formulae by hand. b) word processing which was fixed width and line based, where there would be three characters for 'top of an integral sign', middle and bottom, and you would have to align your three characters at the same horizontal point on three successive lines to make the integral sign, and also position all subscripts, exponents yourself. The fact that LaTeX had an important mission and was successful in it doesn't mean that another thing is not needed now. Things have moved on. Replacing things which solved a problem doesn't mean going back to the situation before they existed.