>

On its own, it is useless. “Hard work” doesn’t get you anywhere without knowing where to work/what to work on.
I agree that people should be in a mindset to be persistent, but I think “God helps those who help themselves” or “fortune favors the bold” may be more applicable. 
Pulling yourself up by your bootstraps is literally impossible, and that phrase used to mean that very thing. From Wikipedia (I know, I know):
In original use, often used to refer to pulling oneself over a fence, and implying that someone is attempting or has claimed some ludicrously far-fetched or impossible task. >

This is going make people pop a forehead vein. >

Agreed. It's a stupid saying to begin with seeing as the original context was talking about literally trying to lift yourself by pulling your bootstraps is impossible, but the meaning behind the phrase can be good advice. The world sucks a lot and it's sadly common to find yourself in tough situations, but no matter how much help you can get, self discipline and working hard can go a long way. >

"Don't tell people to pull themselves up by their bootstraps! Just tell them to work hard. I'm sure that thought has never occurred to them." >

Many if not most work hard. They just work hard at the wrong things. Or they work hard now but didn’t when they were 15-23 years old. Working hard to learn in-demand skills is critical when you are at the age where you actually have the opportunity. >

We're not rolling our eyes at the idea of persistence or hard work.
We're rolling our eyes at the fact that you think this is a novel or brilliant idea, at least enough to bother sharing.
It communicates a level of out-of-touch self-aggrandizement that is laughable. >

In my experience hard work means being used by people. Sure that you can do the job. But don't go out of your way for your employer. Don't give up free time. And if they ask you for a favor you get something in return. There is exceptions to this however. But for the most part put yourself first. >

We're rolling our eyes because whoever is suggesting is implying we are all lazy bums waiting  for a handout. Yeah,  it's a good philosophy that most us are already trying our best to do. 
Of course there are exceptions, and sometimes some tough love is needed to give  someone a kick in the butt, but that needs to come from friends and family,  not strangers on the internet. A whole internet diatribe about "people need to...." like that's the only problem out there is just lazy thinking. >

I absolutely agree! >

"It's a cruel jest to say to a bootless man that he ought to lift himself up by his own bootstraps." -Dr. Martin Luther King Jr.