My thought as well - it's jarring at first to get used to, but Desmos' way of typing in equations, where keypresses really act more like operations on the equation than raw text input, gives a natural easy way to write good equations.

At the very least, typing / automatically makes a fraction with separate top and bottom input areas - which means that brackets for numerator and denominator aren't necessary.

Desmos's input is done with an open source library called MathQuill: https://github.com/mathquill/mathquill