The purpose of the tool wasn’t to make grouping more social. Not having Dungeon Finder means not having cross-realm, automated grouping, which would decrease the likelihood of running into the same people on your own server multiple times over the course of days or weeks, creating shared social experiences.
I never used the LFG Bulletin Board addon, but I did have a lot of people whisper me 5-10 minutes after having formed groups during TBC. I’d ask them, “Are you using some kind of addon?” and they always said they were. I’ve heard that it’s supposed to refresh often, but it seems like it’s caching old listings, which personally I just found annoying.
Keep in mind though, I used to mostly make groups, and never really join others’ groups. Now though, with the new tool, I’ll often just list myself while working on some quests. Especially while leveling, when groups mostly need healers, and there’s an abundance of tanks.