That is not relevant to the post, which assumes that the reader is actually interested in learning a language. Many (I would say most) high school students are

That is not relevant to the post, which assumes that the reader is actually interested in learning a language. Many (I would say most) high school students are not, and don't invest more than the minimum amount of time required to pass their courses. Yes, if you do not practice regularly (preferably daily), and with persistence, you will not reach a high level at a foreign language. Relatively speaking, maybe math is easier. But that's not much of an argument for math and against language learning, unless you have no actual interests and just want to check a box off a list. To be fair, many (and maybe most) adults who claim to be interested in language learning also end up giving up because they are not willing to put in the effort. Too bad for them, and for you if you find it a "waste of time and money"; I find it far more rewarding than flaunting advanced math knowledge.