In vanilla I cleared AQ20, ZG, and MC. I died on Razorgore. That was the full extent of my raiding. I never saw AQ40 or Naxx or most of BWL.
In BC I cleared Kara and ZA and had killed Gruul and Mag. I killed a boss or two in SSC. I did all of ZA, but was never anywhere close to the mount. After 3.0 I also killed a handful in BT, which doesn't count in my book. I've still not seen Sunwell.
Now I've cleared Naxx, downed Malygos and Sartharion. Most of Ulduar I've killed. The exceptions are Vazax and Yogg-Saron, and I've at least died to Yogg a few times. TotC I've done all of. I've already seen a lot of ICC25; clearing the first wing, Rotface and Festergut, and died a few times in the other wings. On 10-man I've not seen blood wing, but I have killed Putricide. I've never done ToC 10 and barely touched Ulduar 10. I suspect I am afraid of PUG raids.
I can't imagine what I'd be doing now if I'd hit a wall. I cannot imagine still running naxx, over and over and over. Maybe I'd be forced to do arenas just to pass the time. Oh, the horror...
Just for fun, I'm going to end this with a question and blanket statement which ignores individual differences or other perspectives. WoW is split between those who benefit from accessibility and get a much greater value from their $15 than before, and those who whine that noobs get to play the same game as them. Which are you?
12 hours ago