Monoids are learned in high-school, long before people people learn OOP, MVC, or whatever else acronym sits on people's resumes these days, with the difference

Monoids are learned in high-school, long before people people learn OOP, MVC, or whatever else acronym sits on people's resumes these days, with the difference that a Monoid is a recipe that's actually simple and well defined. And they are everywhere, so it makes sense to think about generic code that works over monoids.