Too bad we couldn't go back into time and prove this. I'd bet a substantial amount of money that White Plume Mountain would not be on the all time classics list without those three items. They were some amazing, standout magic items. If you removed them, White Plume Mountain] would fall far down or off the list of classics.
And I wish I could take your substantial amount of money.
No doubt that the coolness of the three magic items contributed to the adventure's greatness, but there was just so much to love about that module. In fact, the way in which you've been talking about it makes me think you either ran it badly or had a poor DM (assuming you ran through it at all). The point of the adventure is that you have been hired by wealthy collectors to retrieve the items for them. That is, you have to return them when the adventure is over. Good DMs would stress the potential implications of a band of "heroes" who intend to disappear and keep the items for themselves.
And even if they DID decide to keep these sick weapons, there is a mighty high chance they will wind up suffering from agoraphobia, a strong desire to convert people to the world's prominent ocean god, and a predilection for committing the occasional murder just to appease the appetite of their perpetually hungry, soul-sucking greatsword.
According to the adventure's intro, the wealthy collectors have promised to grant them "whatever they desire, if it is within their power to do so" if they manage to bring the weapons back. There was always something captivating to me about that offer. It provides so many opportunities for awesome role-playing and a great finale to the adventure. What do the players ask for, and what does the DM think these collectors can reasonably offer?
Furthermore, we have an incredible villain, made all the more agonizingly cool because he never appears in the adventure, which really toys with the players' expectations. Is he truly the 1300 year old wizard Keraptis or just some thiefly poser who is assuming the mantle? Only the DM knows. If it is the wizard, has he gone mad? Maybe he was mad all along. He did, after all, vanish without a trace over a millennia ago into the old lava tubes of White Plume Mountain with his band of renegade gnomes.
The dungeon itself is tons of fun, as intended, with really well imagined challenges, obstacles, and puzzles. It is not merely a randomly generated dungeon with room numbers and monsters. Frictionless floors, bubbling chasms, and inverted ziggurats filled with strange monsters is the kind of stuff you find in here. The adventure really made use of the environment like no adventure prior (or maybe even since). Should we shoot at the giant crab in the bubble room? What if we miss the target and hit the rubbery wall surrounded by boiling hot water? How should we "cross cavern vast, where chain-links rattle?" How can we cross the room we can't stand on? These all resulted in great game play every time I've run it.
It also provides a creepy ending. As the heroes leave the dungeon they hear the disembodied voice of Kereptis (?) thanking them for being so entertaining before throwing two Efreeti (Nix and Nox) at them with intentions to see them off to the "Indoctrination Center."
And finally, we have the most badass poem/note that kicks the whole adventure off. It's pretty much the coolest thing you can write if your a 1300+ year old wizard who wants to mock the people you stole some really powerful and rare magic items from. I can still recite the entire poem from memory, but it was the last paragraph that I always found to be particularly chilling:
I care not, former owners brave
What heroes you seek to hire.
Though mighty, I'll make each one my slave
Or send him to the fire.
Pure balls, Mr. Keraptis. Pure balls.
So, when you say that the adventure is only good because it has some really kewl loot, I feel as though you are objectively wrong. In my opinion, White Plume Mountain has more weight in its 16 pages than Hoard of the Dragon Queen and Rise of Tiamat had in 188.