[EDIT]: I personally believe that humanity has been conditioned to expect, perhaps even crave, a timeline/feed based social network, and therefore a non-feed based social network will be up against a general "expectation" of what a social network is by the populace. This expectation is driven in part by an "addictive" feeling that networks such as Facebook, Twitter, Instagram, TikTok, and Snapchat have fostered over the past decade.
This is from the beginning. Wikipedia characterizes the Beacon episode with: "In general, Beacon was viewed as a mistake because it appeared to be too explicit about the intentions inscribed in its protocol."
Feeds on the other hand feel tedious. In the end, Facebook felt more and more like work and less rewarding.
Such a shame that we all jumped on the Facebook bandwagon.
This is not something negative, some communities were just some witty or funny title and others to have genuine discussions.
You could find very active communities about every imaginable subject, it was super useful just like Reddit, but in a typical flat view internet forum and, most important: in Portuguese.
In the last days of orkut, when all the users looking for the "social" thing moved to Facebook and Twitter, all the activity was in communities because still today there's nothing like that.
After the end, some communities just disappeared, some migrated to own solutions like php forums and some, mainly football related, moved to VK, the Russian Facebook, which also has community forums almost exactly like orkut. I believe that 95% of activity in VK discussion boards are Brazilians, Russiand don't use that feature.
Another thing that was massive in orkut - but still niche as most users didn't use this feature - was community forums. It was great to be able to read and talk about any topic using the same account, in the same website and the same layout. Worldwide, what filled this gap was obviously Reddit, but it's still English-only for most subjects. Also the format is different, Reddit is not a typical flat internet forum.