It all depends on why you want the language.
I learned German in HS and college, did missionary service for almost 2 years in Germany, and worked for a computer company in Munich for another 18 months later on, and have been back a few times to visit. But my original reason to learn German was personal. I found it more interesting than French or Spanish (after 2 years of JHS French) and I was a military history buff as well, particularly with WW2.
(And while they all learn English there, their speaking ability covers a huge broad spectrum, and most of them are not that easy to understand; in contrast to Dutch and Scandinavians, whose English is usually very good and also easy to understand [I have my theories on why and it based on the German market for Hollywood movies and TV to be big enough that most are dubbed, while Holland and Scandinavia are markets too small to usually go that expense, so they are merely subtitled, so most Dutch and Scandinavians grow up hearing US and UK speakers while Germans grown up hearing Germans]).
Spanish and Chinese are probably the two main languages in terms of business. But I have no desire to learn either of them. So I won’t.
I took Swedish for 2 semesters in college plus a bunch of self study of Swedish, and one semester of Norwegian. My roots on my mom’s side go back to Norway, and Sweden before that. So it was personal.
My wife is from Japan. I’d like to learn some Japanese (more than the 100-200 words from my kids picture books) but have not really applied myself much to it because of time obligations. Again, personal reasons.
Why did I go through this whole explanation? Because you should learn the language that most interests you, no matter if it is popular or has business uses. Unless of course you do have specific business needs now.
While Spanish would be useful in the sense that a lot of folks in my area speak Spanish, I have no interest in speaking to most of them and the ones I do want to speak to also speak English. So I have no interest in Spanish. (Again, I relate this just as an example)
So, choose whatever language you find interesting or whatever language comes from an area you have interest in, for whatever reason.
If I had time and resources, I’d like to learn (not really in any order) Japanese, Swedish, Russian, Korean, Hebrew, and Italian. I may get a little more Swedish and some Japanese under my belt in the next 40 years before I die but if I had the time and resources that is what I would do. None of them would be really useful in a commercial or business sense, but would be fun for whatever reasons (except Japanese, which would be useful so I could speak in 1st person to my MIL and SILs and to people when we go to visit).
So, what floats your boat? What really interests you?
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