I played a hunter throughout 2005 (wow came out in January 2005 in the EU, not November 2004), toward the end of the year I did learn about molten core and raiding and wanted to get into it, I applied for various guilds (remember when guilds had application forms lol like applying for a job) had friends in some guilds that were raiding (vouch) but no one was recruiting hunters. This annoyed me a little bit, so I rerolled to priest, I thought, Ill play a class that people actually want. I think I made my priest around november or december 2005 and got to 60 around march 2006, by april/may I had found a guild that were just starting to do ZG and growing to move into MC and 40 mans, for a good few months we could only field 20 ppl.
by november we had moved into bwl but we only did maybe 5-8 raids in there, we killed vael, I think we killed broodlord, but then TBC was like meer month or two away.
in retrospect, I spent a year playing a class that never got to raid. then spent several months leveling a new class. then by the time I did get to raid the next expansion was less than 1 year away. what I learned is that, you can't really waste time smelling the roses too much as everything will pass you by. you just won't get to see the raid content. you won't have enough lockouts to get the gear you need to move into the next tier. we we're like a whole year or more behind the top guilds who were moving into AQ 40 when we were moving into MC, when we moved into BWL, the top guilds on my server, like inner sanctum, they were moving into Naxx. you take this and learn from it and do better next time. TBC wasn't much better, I remember killing Grull and my guild leader saying something like 'we're not going to try that hard with raiding' so they were essentially demoralized by the experience of not making it that far in vanilla wow, I on the other hand was not so easily demoralized so, when after a Black morass run with some randoms, they asked me to join their semi hardcore guild. I said yes and in doing that, made it to illidan just before the wrath pre-patch.
if I had stayed in my old guild I probably wouldn't have even been able to do ssc and Tk. the guild I join in TBC did have some Naxx experience although they didn't clear naxx (not many guilds did) it was a night and day difference going from a casual friends and family guild to a guild that was actually trying to do the content and progress through it to the end. we raided 3 days a week and still didn't make it to sunwell, I think we did a few tries at the first boss but, no serious effort was put into sunwell, even though we were pretty much on the cusp of progression during tbc, we moved into BT around the same time as the other top guilds on the server. so even with a reasonable amount of effort it was still possible to not make it to the end. I don't think I missed many raid locks in TBC, some of the earlier ones maybe but I was full t5 by mid 2007.
this is why the mentality is the way that it is though, the more times you just flatly miss content, reguardless of the level of effort put in, the more it just galvanizes the rush mentality. Wrath was a bit better, but I think Wrath was probably the first expansion where more people actually stood a chance at making it to the lich king. regardless of how much you were raiding, you could have probably raided 1 or 2 days a week and still managed to at least do 10man LK.