*grabs popcorn* now THIS is the quality content I come on this website for.
In seriousness OP, if you're writing this out of genuine concern for people choosing degrees you've termed "useless" then bless your big warm heart. However, if you're studing Economics with Russian/"Chinese" or whatever, it's pretty clear that you'll know very little about what a languages degree would look like, or a biology degree, or one in law, or maths, or any other of the subjects you've listed. The information you've got on those subjects is the same old nonsense touted by sensationalist 'newspapers' that feed off (some) STEM students' superiority and (some) arts' applicants insecurity (I was really hoping for alliteration, but alas): ""If countries are going to win in the global race and children compete and get the best jobs, you need mathematicians and scientists – pure and simple." It's this kind of quote you're referring to isn't it, advocates of STEM over humanities, right?
Wrong. This quote has been absolutely slated for the "pure and simple" method of which the speaker reinforces the entrenched dichotomy between arts and science; there is nothing "simple" about generations of kids growing up and choosing their own paths. We will always have mathematicians, we will always have doctors, we will always have scientists, and Lord knows we will always have lawyers. The Law job market is utterly saturated as it already is, and the opportunities for Law graduates are incredibly poor. So why is it still considered a "good" subject? Because the fallacy you're perpetuating is that the salary of a Law student in 10 years should be equated to the salary of an arts graduate after 1 year.
Looking at a university course comparing site, the "average graduate salary" for economics varies from £32k at LSE, to £24k at Sheffield, to £18k at Manchester. Pretty decent. But for Law, it's varying between £19k and £16k. Does that mean that Law has now become null and void, because the average salary is so far behind economics? Like hell it does! Lawyers earn an unfathomable amount after they get settled in their field and eventually work their way up to become barristers or whatever they do there. Looking again for history or english, it's getting a similar variety from £16k-£21k at Durham for english, to £17k-£23k for history. Does this now mean history and english should be bumped up higher because they have the same starting salaries as law?
The point I'm trying to make here is that salary is a very illogical way to judge a subject's "worth". Hell, any method is a terrible way to judge its "worth", because what's the reason for judging it? Why do you get to judge if a particular subject is fit for studying? People will continue to choose the arts for the same reason continue to choose studying STEM subjects: they consider their subject useful for what they want to do and where they want to go, they're interested enough to study it for the next 3 or 4 years, they're blooming good at it, and they've researched it enough to know what it would entail.
Don't discredit other people's choices because they're not like yours.