I'm following the SEO discussions (and some issues on GitHub) for a while now, I think it's important for Flarum to check the SEO structure, but, I also think that not many developers do know how to implement SEO correctly and I am afraid that it can be implemented in the wrong way or development of these SEO in Flarum will take too much time on updates.
As said before by someone else, even WordPress isn't able to get SEO right while there's a massive community behind it. They only deliver the core with basic SEO and make sure that works, others/companies that are specialized in SEO will create extensions/plugins to make sure things work like they should. At the other side, a simple thing like an unique description per page/discussion shouldn't be that hard to create by default for Flarum discussions.
With many extensions available to download, I think it would be hard for the core team to make SEO work for all extra data that these extensions make available to Flarum. That's why I've created the SEO plugin, to cover different extensions as they deliver different data to topics/pages/user pages.
Core or not?
An interesting question would be: what would be better, does Flarum core need to cover everything, including extensions of other developers, or just the simple SEO part and let extensions like mine cover the more advanced stuff around SEO.
Thinking about integrating these things to the core/core extensions, most of them are only getting updated after a core update (once in a few months). As the SEO part is something important (something that can change on the fly or needs to implemented/updated within a few months) it shouldn't be a good idea to integrate that to the core as it doesn't get a release/update that frequently. Important SEO features (or fixes?) can take a while before they get released to the public. I'm not sure what that will do to the ranking of Flarum sites.
Having a team around a SEO extension like mine would be a better idea to improve SEO more frequently and make releases/updates, but at the moment there aren't any contributions from other developers to the extension to improve SEO or add new features (beside the many many development hours I've put in it)...
So far the perspective from a developer 😃 I'll keep my eye on this topic