Interestingly, the modern notation for exponents (including variable exponents and non-integer exponents) was developed by Euler after Newton's calculus. This modern, simple notation certainly makes it easier to explain the concept to the masses... And apply it in a spreadsheet or something.
Compound interest was understood earlier, too, of course. Thousands of years ago, in fact. But not with as clear and simple notation. It was often made illegal.
To reason with agility in a domain, one must have succinct language (verbal and symbolic) to express and manipulate ideas in that domain. Such domain-specific language facilitates both communication and understanding.
Symbolic mathematical notation was the breakthrough that most greatly increased the rate of mathematical breakthroughs thereafter.
Compound interest was understood earlier, too, of course. Thousands of years ago, in fact. But not with as clear and simple notation. It was often made illegal.