There is not a unique answer to that...Perhaps, because they did roll out the iPad Pro in an attempt to reignite iPad sales which have been stagnating.
Will the average consumer really understand or care about iGPUs and 5400 rpm drives, or insufficient flash storage on the Fusion drive? No, but they will get frustrated when the computer feels slow.
So far the reviews I've been reading have been fairly positive on the iMac, though mentioning the lack of dGPU and the odd reason to use a 5400 RPM drive in 2015 but overall I've not seen a harsh review.
The average consumer surely can't notice the reduced flash storage on the Fusion Drive , due to the nature of the fusion drive itself.
The average consumer can't notice the lack of iGPU, unless he/she doesn't try to play a game at 4K resolution.
The average consumer surely can get frustrated by the 5400RPM HDD performance.
Every review I read so far, spoke quite well about the new iMacs (actually the only one not very happy about it was Ars Technica's you linked yesterday). On forums like this users are whining, crying and screaming about the new iMac.
But I've learn forums like this aren't a good representation of the real world.
My opinion ? Im not going to buy one. I don't like the price trend Apple is taking outside US. I won't buy a 2015 computer with a 5400RPM HDD (Fusion Drive 1 Tb is the MINIMUM requirement IMHO). But overall I think the 2015 iMacs are a good product.