[viridian]

On the ops side, /r/selfhosted and /r/homelab often come up in searches with pretty good content. /r/aws is also okay, but there's obviously also a lot of certification and amazon event noise. On the dev side, /r/reactjs as you mentioned is pretty good, and I can't really speak to any other languages right now, since I've been full stack js for over a year now, and /r/node and /r/javascript are not so good.

[shagie]

I believe it has to do with the specificity of the forum, passion of the people contributing, activity of the mods to keep it "on topic."

/r/homelab (I've dipped my toes into occasionally) has people who are passionate about their craft. The people who are interested in setting up a homelab are also likewise interested in investing (time and money) in it.

This differs from things like /r/learnprogramming where the people posting are not invested in it (the community or the craft).

Another difference would be the "who contributes new posts" aspect. With /r/homelab new posts come from people of all skill levels. With /r/learnprogramming they come from people who are at the very basic skill level.

The implications of this is that /r/homelab has peers helping peers while /r/learnprogramming needs people who aren't posting questions to post comments and provide additional material.