The headline says researchers but it makes more sense if you name the progressions.

Most researchers start their careers as graduate students. Graduate students are poorly compensated and, despite the name, very little support or good advice for their advisors, on average. They receive plenty of negative feedback and insecurity, though.

Then graduate students graduate (or drop out), either with a Master's or PhD. At this next tier of employment they either do a postdoc (basically just doing the last 2 years of a PhD again but with even higher expectations) or join the private sector. Neither the public sector nor private sector have enough positions, let alone well-paid ones with acceptable work environments, to take on the number of graduated graduate students each year. This forces many out right off the bat.

If someone continues to try to become a professor after doing one or more postdocs, this difference becomes stark. There are between 10-20 postdocs that want to be professors for every open professor position.

If someone goes the private track, (1) most of your explicit training goes to waste, as your environment was academic and all of your advice came from the 1 in 10 postdocs that got a professor position, and (2) you now get to try and navigate corporate petty bureaucracy in addition to doing work for whatever the company's lords deem profitable. Many burn out rapidly in this environment, as while you actually tend to get paid and treated better than a graduate student, this usually comes at the cost of losing all motivation for the research itself. And when you want to advance your career, you get to learn the basic corporate lessons that everyone else does: you can't advance much within the company because an incompetent boomer that is friends with the CEO is sitting on the position you want and even if they weren't, the company sees no advantage in paying more for an employee they already have. That's money they can't use to "snipe talent" and "reinvest". So again, the positions available dwindle through that path. So instead you end up making a series of external moves, sometimes purely lateral. You might even find a company where you live the research, but it will almost certainly then be one that offers you worse pay and advancement opportunities. This is usually because the most appealing research has a socially positive impact (or at least rationale) and the companies doing that research know this and adopt a non-profit "sacrifice yourself for the cause" paradigm that, naturally, does not apply to the C suite.

If you are a researcher that didn't go to grad school, the system is the same but they put career advancement caps on you more quickly and often, regardless of how skilled you actually are.

Oh, and I almost forgot: God help you if you are minoritized in any way. Academia has no real workplace standards, they let people at all levels get away with sexual harassment and discrimination all the time. The usual status quo is that nobody wants to know what a given professor did to a student. They don't ask and they don't do any real follow-up to reports. So your experience as a graduate student or postdoc is dictated entirely by whether your advisor is, of their own accord, a good person with good advice and no unseen vices or bad habits. The corporate world is obviously little better outside of the threat of a lawsuit or state investigation.

So, reviewing this, we can make some conclusions:

• At every step on the career path, you are expected to accept questionable pay and working conditions so that you can get slightly better ones at the next step. But there are not enough positions for most people to actually reach the steps they want to. This necessarily leads to dropout.
• The environments themselves are not great due to a glut of workers, there is a large reserve army of labor to do these positions.
• The system functions to maximize the size of this reserve army labor pool through media and communication monopolies. There are very few ways for good career information to get passed to students, postdocs, etc. The only people they ever hear from at the "next level" are the small minority that got into the higher positions. If you had 15 postdocs that didn't become professors telling you it's a scam vs 1 professor telling you that you just need to work hard, there would be fewer applications to grad school.