Ok, you managed to get enough competent people together to win the 25 schedule management game (which is honestly the hardest part about raiding), congrats (no, genuinely congrats, I can't raid 25s anymore because 2/3 of my guild has jobs that no longer allow for that kind of time commitment).
But are you honestly saying that you preferred the shaman, shadow priest and warlock stacking TBC WoW of the past? I mean, that's really the only significant difference between WoW now and WoW then if you're on the cutting edge. Now you don't have to stack your raid to such an extreme (sure, raid stacking can be beneficial in a couple cases, but not like that was) in order to simply compete.
Yogg+0 is relevant (or was, anyway until people seriously get in to 3.2 encounters in a few weeks) because it is still a challenge that you haven't conquered (if you were still raiding, at any rate), and I assume that you say the game is boring because you don't find it challenging anymore. To say it's not relevant is to entirely miss the point.
I disagree with your statement that it requires no thought, skill or strategy. What it no longer requires is having enough alts of the right class to stack the raid. Skill, thought and strategy and the class you like to play already being ready to go is why things seem easier. No longer forced to grind alts of a certain class, swap people left and right for a different spec. It was stupid and it wasn't fun. You're lying if you say it was enjoyable to hearth, respec, and come back to the raid between boss fights. That's what TBC raiding was and that's what is gone with WotLK.
Do you miss the massive attunement chains? I don't. I don't miss dragging people through them to find out half-way through they couldn't commit to the hours, or simply didn't play as well as they claimed. Now I can kick them after the first boss fight without any significant investment loss on my part.
Yes, it's more casual friendly, but the challenging elements aren't gone, they just have fewer annoying logistical elements that almost no one enjoyed. How does a bad player picking up a handful of purples from a new 5-man affect your experience?
As for "couldn't kill Yogg+4 killing bosses in coliseum", so what? People who could barely get Kael'Thas would roll over the first 3 bosses in Hyjal without even blinking, yet you hail that as the pinnacle of raiding. That's not to say the design of the entirety of 3.2 content is good, I just don't think it supports your points. From a lore progression perspective it seems dull and lazy.
If you really did enjoy that, then maybe WoW isn't for you. Perhaps EQ or UO is more your thing. It takes all kinds and I'm told EQ is fun, I just couldn't get in to it myself.
Honestly, the "casual v hardcore" argument is tired and pointless. Both play the game, and Blizzard is catering to both equally. The biggest difference between the two is that 'hardcore' is always a temporary thing that keeps moving up, as it has been and as it will continue to be in games like this.