I'm the exact opposite, I found the shimmering flats/mirage raceway to be the dullest part of the zone. It's just a big, expansive, flat and boring pancake with atrocious quests like going around gathering 30 rocket car parts. The needles section of the zone is by far the most interesting: Running around the bases of the spires, climbing them up those twisty footbridges (since we couldn't fly) and fighting atop them on the footbridges, a colossal drop below the planks.
I like the new zone too and overall the quests are more interesting, BUT it makes me kind of sad that basically 99% of the zone is flooded underwater. All those centaur caves and villages, hidden away underwater.
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Redridge Mountains - Landscape remains more or less similar, but quests are far better. Love the J.J. Keeshan series.
StV - entire experience feels more streamlined, lots of the spammy quests toned down, less running back and forth doing Nesingwary stuff (though sadistically I did enjoy collecting all the missing pages!) and love the new quest chain that sends you inside ZG, have you tried that?
Ashenvale, Stonetalon Mountains - The zones are just WAY WAY better, especially Stonetalon as Horde with the whole Krom'gar thing. Get to drive a siege engine at the end and wreck shit up.
Western Plaguelands - Andorhal is just better in every way. Landscape is largely unchanged, but I do miss the cauldron quests.
I could probably come up with more examples with ease but I'm running out of time for now. The point is, plenty of zones were improved in Cata. Well, IMO obviously. I'm sorry to hear you're so difficult to please. And yeah some zones got worse (Hinterlands for example, they ruined Jintha'alor) but generally the zones are better, flow better, have better quests. Even Swamp of Sorrows is better with the whole Stonard vs. Whatsitcalled battle thing going on.