There's some rose-tinted goblin welding goggles there.
Pugs for 5-mans used to be a huge pain in the ass. Especially for lower-level dungeons or for DPS classes (and especially the boomkins, the fury warriors, and the ret pallys).
Remember spamming city chat, LFG BFD?
And if you were a warlock, you were expected to run all the way there (remember not getting mounts until 40?), and wait for two other people, so you could summon the last two?
I haven't really played much since TBC, or at all since LK. LFG was a huge improvement. It had flaws, for sure...it did break the community a bit, as you said...but it made the game playable for people who didn't have hours to commit to getting ready for a 5 man dungeon.