I've only gotten up to doing an MSc (currently volunteering for Vikash Masinghka in my Copious Free Time), but I do know a hell of a lot of academics.
From my (second-hand) knowledge, easy quals are an artifact of something very like economic privilege: your school is very prestigious and doesn't need to cull its grad-student herds as much as others, so quals are allowed to be easy. In other places, quals are used to evict many grad-students from their PhD program because resources are more scarce.
but it seemed like MIT grad students also often started doing research fairly early on, from my perspective as an undergrad there.
I don't know anywhere where grad-students don't start doing research as early as possible. Do some programs really involve whole years of just classes?
Absolutely. It's a function of grant money. MIT has more grant money than anyplace else on Earth, so it's easy to start grad students on research projects. At the U. of Buffalo, there were only 2 professors in my department who had grants, so getting onto someone's project was hard, and anyway you were taking 4 classes a semester and TAing at least one for the first 2 years, while studying for the qualifiers. I don't know anything about this "free time" OP talks about.
Few students did research before their third year, after passing their qualifie...
Among my friends interested in rationality, effective altruism, and existential risk reduction, I often hear: "If you want to have a real positive impact on the world, grad school is a waste of time. It's better to use deliberate practice to learn whatever you need instead of working within the confines of an institution."
While I'd agree that grad school will not make you do good for the world, if you're a self-driven person who can spend time in a PhD program deliberately acquiring skills and connections for making a positive difference, I think you can make grad school a highly productive path, perhaps more so than many alternatives. In this post, I want to share some advice that I've been repeating a lot lately for how to do this:
That's all I have for now. The main sentiment behind most of this, I think, is that you have to be deliberate to get the most out of a PhD program, rather than passively expecting it to make you into anything in particular. Grad school still isn't for everyone, and far from it. But if you were seriously considering it at some point, and "do something more useful" felt like a compelling reason not to go, be sure to first consider the most useful version of grad that you could reliably make for yourself... and then decide whether or not to do it.
Please email me (lastname@thisdomain.com) if you have more ideas for getting the most out of grad school!