Good advice in general, but not a hard rule. There are roles where you need to expend a lot of energy learning proprietary stuff (processes, languages, frameworks, business rules). If you're in one of these roles it can give you a ton of leverage, but tread carefully around egos (you could get fired out of spite if you flex too hard, and maybe that's fine, but generally it's lose / lose).
You're right, of course, with just a nit of misinformation here that always bugs me: there are still lots of places that have pensions, just not places the HN demographic considers worthy of working at. I have one from my time at IBM, one from my telco days, and my current employer (financial) has a pretty generous one.
I've also had a company get acquired by private equity. I got nothing for my shares and they shut the team (and the product) down within two years.
Worst case scenario would be employee stock options and RSU grants remaining or becoming worthless, like in the case of a private company that never gains enough traction to exit or exits at a low valuation.
Usually in a public acquisition, shares are purchased at a price premium.
E.g., many Twitter employees got to cash out at a stock price well above the value of the company.
Every employee should see their role as temporary. This isn’t the lifetime employment pension days anymore. I see many opportunities for employees to walk away as a positive.