It is a challenge but it can be done if we as a community can work on it. Why are you concerned about SEO? This is where I surrender as the SEO part is so much destroyed as Reddit stands out when typing anything related to understanding Bitcoin or its issues. What you said is another excuse as the community is still progressing with mouth recommendations or due to the reason that the forum does not provide good informative post anymore.
I don't think decentralized forums can work now. There isn't anyone working well.
Seo is important for traffic, which is important for money and sustainability of the forum.
Bitcointalk seo is very good, and there is very good content here. I found many times posts of this forum appear in my Google searches.
And reddit is a very good forum with many good information. Not the best for crypto , but there are many other subjects there.