Watching all of these Nostalrius rant videos, that often go on a tangent on how great WoW was from Vanilla to the WoTLK days. The reality is Blizzard can't just remove things like LFR or LFG that hurt the community, but I feel like there are ways to compromise around them, for the better of the game.
TBC - Flying
That's the only blunder of that xpac that had any long term effects. Personally I don't think Flying in WoW is that big a deal, it didn't totally kill World PvP it just made it more optional. Daily Quest hubs could still turn into a skirmish if not an all out War zone, especially Isle of Quel since there was no flying. A problem that began to start in WoTLK is we slowly lost a reason to ever land, something they're hopefully fixing in Legion. I think WoD with no flying would have been a success had there been a reason to leave our Garrisons. I had a lot of great times on the ground early WoD.
People want to use there flying mounts fine, so how about you can only access your flying amount at a flight master. you can mount up around the flight master and fly where you please, but the minute you dismount your grounded, unless your near another flight master.
WoTLK - LFG, Inflated Economy
I remember when LFG first came out and I loved it! However as time went on I slowly realized that the game was starting to feel more like a Dungeon Crawler then an MMO. The Looking For Group tool is a more proactive experience where your likely to have to interact with people before inviting them or getting invited. I say just keep LFG around for leveling only perhaps since it's harder to find a lowbie group, if that at all.
I really have no answers for the inflation that started when WoW streamlined the crafting, and Garrisons only made it worse.
Cataclysm - LFR, Paid Faction Changes, Transmogs, Leveling(I know I'm missing something, Cata was a dousy!)
LFR has it's place in the game, but it can be implemented far better. Blizz releases it about two weeks into the tier. I feel that they should release LFR of the current tier two weeks before the new tier! If you think back to TBC by the end of the expansion Blizzard nerfed all of the content by a flat 30% that way players could see as much as possible before WoTLK. In WoTLK we had the 30% buff in ICC so most people could probably at least reach and fight the Lich King.
The leveling experience needs to be redone again entirely somehow though, for the sake of fresh new players. No idea how anyone would stick around as it is now due to how unchallenging it is and never needing to group.
As LFR is right now it just doesn't motivate new would be raiders. When a new tier comes out people should be excited to jump into and get ahead of the curve to experience can, not just sit on there heels waiting for the tourism mode to come out a few weeks later. It shouldn't function as a catch up mechanic at all anymore either, or at least not a full catch up mechanic. There are better ones out there.
Xmog has it's pros and cons, it can stay.