Very few people want to be scientists. To see why, just replace "scientist" with "nerd", because for most people those are synonyms.
Moreover, anyone who wants to do science can become a grad student. That's at least 5 years of "basic income", and access to mentors/tools/resources. All you have to do is to find a lab that does what you're interested in.
My friends in the natural sciences are more tied to the projects of their supervisors. But in the end they are still expected to be a mature researcher with their own agenda.
Caveat: I'm only certain that this is true for top-50 programs.
A grad student is an apprentice. This article is about a less taken path for a master. As a former PhD grad student, I can say most grad students are not in a position to conduct independent research. Most get attached to some funding obtained by someone more experienced than them, and then spend most of their time getting up to speed until they are able to write their own papers on that topic. But this leaves them a very narrow set of skills. This is why most academics go through a postdoc.
As long as that topic is what they would like to research, I don't see a problem. And if it's not, then they chose a wrong lab/advisor.
But this leaves them a very narrow set of skills
I developed a pretty wide range of skills as a phd student. From developing device models in Spice, to Tensorflow. In fact, I wish I focused on a subset of those skills.