The claim isn't you should shut down your blog and only talk on GitHub to be engaged with the community. Zig has tons of communities https://github.com/ziglang/zig/wiki/Community and, of course, blogs also play a part in the overall community too. Picking a single engagement option is probably always a poor choice, but that option being your personal blog alone would be one of the poorest. That's where the feeling of lack of collaborating with the community is coming from, not that they specifically don't engage in GitHub alone.

Make blog posts, it's great!, but if you don't think you're the expert then they'll go a lot farther for everyone if you put 5% of the work of doing so into engaging with the community about it for additional insights first. That's a fair note to make, though I agree the ending could be less passive aggressive about those who don't want to engage with the community.