If I put you in a dark room, and ask you to find a way to light it, how many times will you fail to find the switch? Oh wait, I lied. There's not actually a switch, but there might be a candle in that general direction. Maybe.
That's how little we have to go off of. That's how empty any information on your study is. I don't think people really understand how hard this type of work is.
Research is a purely exploratory and creative work. Like art, science requires time, patience, and many many failures. You don't just get a bunch of eureka-Einsteins that come out of MIT day one knocking down Theorems and discovering new physical laws. That's just not humanly possible and it's ridiculous if you think it'll ever work that way
I am perfectly willing to admit that the vast majority of research and PhD's went nowhere and will continue to go nowhere for a long time. But that doesn't mean they're useless. Research requires exploration. It requires trial and error. It is highly inefficient and does not fit well in a consumerist society like ours, but this is the way that works best for us so far.
If you have some better idea, then why don't you go out and do it? How are you going to get a bunch of incredibly intelligent, creative, and independent people funded and provided for in a society that values immediate results over long term achievements?
I'm not arguing the academia system is perfect. Any one knows it's screwed up beyond belief. But it's not out of malice. We're not purposely trying to make the world worse, or something ridiculous like that. You have many people who care a lot about the science, who need to eat and sleep and need money to do that. Sometimes the money goes to their heads, sometimes their massive egos get the better of them, but do you seriously think we don't care about science? You'd have to be an idiot to do a PhD for the money or the fame. Why do you think we put 7+ years of our lives into stuff like this?
So most PhDs don't actually get tenured positions. What are you actually trying to say? Are you saying there aren't enough tenured positions? Or are you implying that these PhDs don't deserve tenured positions? Do you have any evidence for either of those claims? Because otherwise you're just participating in more armchair speculation.