I'll go one further than Newbie.
Regularly accessing the latest content requires one of two things:
1) Being in a guild which is capable of clearing that content.
2) Setting up a schedule with other players, so that the group of scheduled-but-not-guilded players can make regular attempts at the content.
One can not generally assemble 25 people picked at somewhat random, take them to a "new" raid, and expect to make reasonable progress in it.
I intentionally specified "regular" access. There are the odd lucky people (typically "significant others" or friends of people in a guild) who will get carried through content and get to experience it. Getting to see Icecrown once would not necessarily require being in a guild.
People carried through a place from time to time get to experience the visuals of a zone, but given the existence and spread of loot drama, I'm wagering that players also have other motivations. Satisfying these (OMG BEST IN SLOT) cravings is what locks players into #1 and #2 above. Having to do via a primarily random reward delivery system (feral staff AGAIN!?) ensures it takes a good, long time.
There are several schedules of reinforcement that can be used in Operant Conditioning. The most basic is a fixed interval schedule, and the rat in the Skinner Box is rewarded every 5 minutes regardless of whether it presses the lever. Unsurprisingly, this method is not particularly effective. Another kind of reinforcement schedule is the fixed ratio schedule, and the rat is rewarded every time it presses the lever 5 times. This schedule is more effective than the fixed interval schedule. The most effective method is a random ratio schedule, and the rat is rewarded after it presses the lever a random number of times. Because the rat cannot predict precisely when it will be rewarded even though it knows it has to press the lever to get food, the rat presses the lever more consistently than in the other schedules.
There are plenty of successful groups I know that have less than 4 raid days a week, in fact.
This is ambiguous to the point of worthlessness because "successful" is vague (all "hard mode" content down?) and because it leaves out how many hours they raid on those days. (E.g., 5 days a week for 3 hours is (15h total) is less raiding than 4 days a week for 4 hours (16 total)).
See, I love me some endgame. But I hold no delusions. The quality of your endgame experience is directly related to the quality of the people you play with.
...where quality is probably strongly correlated with how much time the people invest in the game, be it playing ("gear=skill" jokes aside) or reading up on fights.