You chose your server.Wait what? CRZ allow for far, far, far more people in every single last zone than ever before. CRZ means that you're not just fighting your own server but people from dozens of servers. There was no flying in Classic.
People complaining about being unable to level, at all is actually a valid complaint. There are certain zones where leveling is completly impossible on a lot of battlegroups because the level 90 gankers outnumber the questing people by 10-20x. Blasted Lands, Hellfire Peninsula, Hyjal and Vashjir. The people going around ganking from what I could see so far are mostly PvE scrubs. They are people in horrible gear who get stomped in competitive PvP and thus have to take out their frustration on low level who can't fight back. They have no idea what real PvP ist for the most part.
In all honesty, hiding behind phasing to gank low levels for hours completly locking down without anyone being able to do anything because nearly all 90's are in a different phasing zone has nothing to do with world pvp. It's griefing and sadism, plain and simple. And if you actually hunt down these PvE people they either mount up and just hover over you till you eventually leave because they don't stand a chance or they log onto your server and start flaming you.