Being in a position to point out the privilege of another is itself quite a privilege.
There is rarely a suggestion given in modern society that doesn't assume a good amount of privilege, and pointing this out every time isn't helpful.
I welcome suggestions that can help those who cannot simply quit, but you didn't give such a suggestion, which is why I say it wasn't helpful.
Accusing people of privilege is a dead end. A person who has been accused of privilege is left without direction. It is better to say "what about these other people" than to say "you're privileged", because it directs attention to the other people. It avoids accusation and focuses attention on those in need.
Somewhere on this planet is a single individual human who is the very unluckiest and most unfortunate. Everyone else is privileged. Even that guy is lucky to be alive now and not 1000 years ago.
Calling out a solution as "privileged" adds nothing to this site.
You have a job at all? You have the brain and attention span to read this far? You can use computers to solve problems? That's a privilege. And yet we don't point that out every time a programming or career or product question is asked and answered.
Perhaps OP could have added something a bit gentler like "quit your job - if you can". But it's fundamentally a sound plan for many of us, and crucially, also even for many of us who aren't aware how much market power they really have.
Is it okay to post suggestions that only apply to a small portion (say, 5%) of HN readers and trust people to determine for themselves whether or not the advice is applicable?
Yet, it doesn't mean that quitting is always going to be the solution. There are specific conditions that need to be met (sufficient savings, decent possibilities to get a similar job, and so on) in order for quitting to not hurt you financially and professionally. Yes, everyone can be seen as "privileged" if we compare our lives to how it was back then, but that doesn't dismiss the issue.