The Python Development Category is gone.
Devtalk is a place for Blender developers to reach out to other developers and get help developing Blender and a place for Blender developers to reach out to the community and get feedback on ongoing work.
If a developer likes to improve the Python API, questions can be posted in the “Contributing to Blender” category. If someone likes to get feedback / support on how to use the API, or has suggestions (feature requests etc) you can for example post on https://blender.stackexchange.com/ or Right-Click Select — Blender Community
Blender Stack Exchange doesn’t provide topic-driven content in threads, and Right-Click Select doesn’t have many developers. I don’t see a reason why this category has to go to Archive and be Read Only.
It’s to keep this forum focused on what it was created for. Broadening the forum definitely has advantages, as you described, but it also has downsides.
The wider the use, the more different people are on here discussing different things, the more pressure on the moderators to keep things friendly and on-topic.
At some point this got out of hand, and it was decided to re-focus devtalk so that it’s as useful as possible for all Blender developers to support them in their work.
That’s a bit of the reason why, as far as I’m aware of.