The way the score is calculated is hidden from the public
I mean.....technically, I guess, the specific parameters are hidden? But the meaningful actions - the ways in which you can improve your score - are extremely clearly advertized.
Don't get me wrong, I'm not exactly a passionate advocate for the system - but it's nowhere near as obfuscated as people claim. And if you accept the premise that there needs to be some algorithmic way to evaluate someone's creditworthiness, "their past reliability in repaying debts" is a pretty reasonable choice.
the ways in which you can improve your score - are extremely clearly advertized.
They are for the "credit score" they give you. There's dozens of different credit scores that different lenders pull though. Ones that are specifically curated for their needs and that you'll never see.
And it's not just Americans either. At least in Germany we've got credit agencies that rate you with their secret algorithms. Got a bad score? Sucks for you!
I don't know about having to take out loans to improve it though. I think that does the opposite. I'm not an expert, correct me if I'm wrong.
Having ongoing loans might be negative although something like a mortgage for a house you bought with bank assistance typically won't. You aren't expected to take out loans to establish your reliability.