There are, indeed, a great many things I miss. Some of them I get to see whenever I want, like Blackwing Lair and Un'Goro Crater, others are players who stopped playing, playstyles that are no longer valid (I loved and will always fondly remember the days of fury tanking Stratholme for my guild Eldritch Way over on Kilrogg, then taking the technique into raiding on Azjol-Nerub with Sworn, fury tanking in MC, BWL and AQ before finally speccing prot to tank Naxx) and even places that are just plain gone now. The other day, while doing my weekly scouring of the Barrens I realized that ever since Cataclysm, the zone I remember is gone, baby - Mankrik's wife is buried, and the days where I rolled a horde and leveled it to 60 just so I could attack my own guildmates when they raided the Crossroads are just as buried as she is.
All this is fine in and of itself. It can even be healthy for the game - memories of good times had playing will sustain when nothing can truly be said to be new anymore. I personally find it very difficult at this point, when playing any mmo, to not compare current fights to previous ones I've done. Having seen pretty much every boss available in the game, I speak a shorthand made up of phrases like "he spawns adds in P2, it's like Rag" or "if you remember Lurker, it's like that". There's a line between being blinded by the past - for example, trying to argue that raiding is easier now - and making use of it productively.
There are absolutely parts of the game's past I miss, and would love to see again. I miss my ranged weapon slot. I miss when some hunter pets had weird attack speeds or did shadow damage. I still kind of prefer 40 man raiding to 10/25. If I could tank a dungeon as a fury warrior, I would be tanking all the time, because that's still my fondest memory of tanking in the game and I won't lie and pretend otherwise. I understand why the changes were made, and in many cases I can agree that they were for the good of the most players. Did I ever seriously play with that arms dual wield spec? No, I didn't. Do I really think it would be feasible to try and maintain a 40 player raiding roster? Heck, I don't think it was really feasible then. Half of the difficulty we had raiding in classic was getting people to show up, and half of the remaining difficulty was getting through raids with at least 10 players who never knew what was going on. Different raid groups called it by different names, but it all boiled down the same way. There were raiders you only kept around to hit the 40 player mark, who contributed nothing, soaked up loot and churned away once they were done.
This difference between fond remembrance and willful drowning in the past has to always be kept in mind, and managed. The reason the game has changed and changed over the years is in response to us. As the player base changes, so does the game it plays in. Every feature, every new raid, every new dungeon, all content and systems deployed were put in for us. Even CRZ and the upcoming virtual realms exist to address a consequence of the game, which is why we don't often see player feedback lead to immediate revocation of an idea or feature. This is for many reasons - player feedback doesn't always add up uniformly, it comes in many forms (not just forums and blogs), and even if a feature or system is roundly disparaged if it exists to address a problem, it's much more likely to be iterated upon than removed as long as that problem still exists to be addressed. It's easier to make changes than to scrap and start over, after all. Think about armor penetration or defense on gear - these stats endured for years before they were removed/replaced because changes that big require time to roll out and test. Defense in particular is a stat I remember having to address over and over again in my time writing about the game, a stat no one seemed to understand on first playing the game.
Did people pick it up? Absolutely they did. Players are amazing that way. They can and will learn and game the most advanced systems if left to their own devices. Someone will come up with ways to use new features like reforging in ways no one foresaw, someone will sit down and work out all the math on how defense works, someone will calculate haste caps. All of these things are part and parcel of the game's evolution. The game changes, we change, and we change the game right back. And it will continue to do so. Looking back is fine, even healthy - it informs us as players, it helps us decide what worked the best and what didn't - but you can't live back there. It's buried with Mankrik's wife.