EDIT TO TRY TO EXPLAIN A BIT WHY I'M ASKING:
1. The fight before that took some 40 days for the top players in the world to beat. It was kind of a big deal at the time.
2. It was the first time they'd had an animation like that.
3. Back then, seeing a new boss model was a really big deal. Even in TBC only so many people had seen this boss. Seeing a new boss was a milestone for any player back then.
Not trying to be a condescending jack***, but do you understand now? If I had just said "Remember the first time you saw Sapphiron? Have you felt like that lately?" - then it wouldn't be referencing seeing a new model, a new boss, a hard boss to reach (Heroic-only mode, basically, back then). In WOTLK that was a boss model that was widely re-used outside that raid, and it wasn't a special thing to see him. There was no "OMG guys, we're at SAPPHIRON!"
Even in TBC, on my backwater server, Kel'Thuzad only went down twice, afaik.