The real loss for the internet is the puritan approach to federation and decentralization. It's either that or app-centric solutions like matrix. Even forums weren't discoverable easily. I'll say this, matrix really has the right idea, it just does too much too fast. An SRV DNS record indicating your matrix server should be enough, then browsers should auto-discover the 'matrix' for the website, and via matrix you can comment on a site, leave reviews, chat with visitors, post forum-style,etc..
But as I mentioned in another comment, what's more important is how easy it is to administer and setup. The experience for site/community owners is the critical factor for adaption.
Based on how search engines behave to day, not really. These days, you'll have to fight spammy forums who game SEO, reddit, stackoverflow, ML digested output,etc.. it is discoverable as in technically it is somewhere in the results, but people never see it. If google paid discord like they pay reddit and searched discord servers that allow for that, that might be a nice compromise.
Also, ancient forums without https seem to be excluded by Google more often than not. I know they have their rules to push TLS but I still want results regardless.
Add forum or “forum” to your search term and you’ll get results from tons of forums. Yes, you have to know to do that, but once you do, your results will actually be good.
But as I mentioned in another comment, what's more important is how easy it is to administer and setup. The experience for site/community owners is the critical factor for adaption.