They are doing work, they're advocating for what they believe in. Consumers of FOSS deserve to have a voice too.
I think the op was suggesting the contribute to FOSS rather than shaming people who have contributed greatly for not contributing more.
It's easy to advocate for what you believe in by posting comments on HN. It's harder to advocate for what you believe in by taking a low-paying job in a FOSS company, which they presumably didn't do.
If you see complaining on forums and maintaining software as contributing the same kind of value, then oh boy do I have an enterprise-grade comment thread to sell you.