Luckily the web isn't a zero-sum game and people can create sites even if similar sites already exist.
That makes sense of there is an actual difference, or if the creating is for learning only. Given that the post said nothing about goals, I'd like to know.
Although if the goal is community, the game development community feels fractured enough (in terms of sites to visit) as it is.
Yes. But if you offer nothing different or better than the competition...there's no reason for anybody to care since their needs have already been satisfied.
Note: I'm not commenting on the merit of gamedevs.com itself.
Neither are very good or useful for professional devs?
Upvoted because it's true.
However, it is unlikely an HN-style site would fare better. But who knows.
gamasutra.com is more like industry journal with its own content. It is not a news/blog posts agregator. gamedev.net and gamedevs.com seem to be closer to each other.