I think there may be some who breeze through grad school, likely by being in a strong research environment beforehand, or by having lots of support. I mean, they have to exist?
Have I genuinely met anyone like that? Nah. And, oh boy, can it be a struggle!
During a PhD, it's very easy to put yourself into an increasingly hopeless situation that is mentally tough, for years on end, and it is really hard to even convey to anyone outside of academia why you would do that.
It is especially hard to convey to people outside of academia how 5 (nowadays often 6,7, etc) years of work all come down to a few, often seemingly random decisions of hiring committees and other structures.
You start grad school thinking it's something you build, bit by bit. At then end, it's more of an ever shifting collection of you, put together in the hopes it will be evaluated well. But then you realize, it really has little to do with objective quality, and much of the situation is outside of your control. There is no short project in grad school. It's the entire thing!
I think the worst thing is the uncertainty about literally everything. Is your Professor ever telling the truth? Will you really get that support two years out? Will the funding persists? What are you even researching?
I have seen people had the work of the past five years ripped apart during their thesis defense (or wherever), I have seen people make a few missteps and ruin their chances on the job market. I have seen people invest a lot in work that never makes any impact. I have seen people who thought they'd make Professor, and then found they have zero motivation or talent for research and/or teaching.
You can never be sure that ain't you, until you have your PhD and your job.
It's always on your mind. Projects aren't short anymore, you work years on stuff before it ever becomes a paper. You work every waking hour and often every sleeping hour as well. And you lack the knowledge and experience to assess whether what you are doing will really go anywhere, if the network you are building is right, if the people you write to will be interested in your work. At the very least, you never know who else starts with you and will compete with you on the job market, which is increasingly filled with people willing to work for little money and little job security.
In the past two years, academic positions dropped 70% or more, at least in some fields. And we have 2-3 cohorts of applicants on the market due to Corona, and this will remain for years.
Academic research nowadays requires nerves of steel, and I have seen grad school ruin the health (mental and physical) of quite a few people, all of them very good at what they do.
So after all that doom and gloom, people need to realize that it is a struggle for probably everyone. But it is also rewarding, or it can be.