I would simply put it as it takes some time for general public to accept something completely new from scratch that is an engineering marvel good enough to be in the same if not beyond league of Ferrari. Lamborghini is not in F1 so the only worthy competitor roadcar would be McLaren.
It is just not easy to for all to accept that a car company can come up with something so ground breaking. It changes everyone's thought (Carbon monocell, brake steer...) about a road car. Technology wise, Ferrari is using a winning formula (like the 911) and evoluionizing it basing it on a successful blueprint not to be messed with. McLaren uses revolutionary F1 technology and completely new blueprint to build a car. It is new, with all in house parts no in house parts. There will be glitches but it is definitely as iconic as the 458 if not more as the one and only iconic supercar in this era. It will also be the first to mark automotive history of supercar at the dawn of this decade.
I would simply explain this, regardless of what magazines say, the car is an admirable engineering piece that is very different from a 458.
I maybe wrong but in terms of technology and racing heritage/elements (carbon shell... etc), this car has as much as if not more technology than 458. Comparing to a Gallardo, I would say this car is 2 - 3 generations ahead.
However, the caveat in taking on something so new is that you will have to take risks. Reliability, sales, second hand value all unproven. Most important, when the car was so expected, people have very very high expectations and I think it will take a long time for the press to digest and really understand the car as an automotive history icon. It takes time to warm up to something so new and so different. In the past, people only pit Lambos against Ferrari but now there's a completely different, techno, special company making a car so worthy and yet, the car is also made by someone and a marque who had a rich history in Formula 1 racing. It will baffle people.
I wouldn't deny that it is going to be an upstrem battle for McLaren Automotive because it is benchmarked against the best, the red pony. However, I am split as well in taking on a less visited path (I am suspecting that many are already pulling out).
I am still 50/50. When GTR comes out, it was very controversial and then the R8 as well. It takes time to accept something special (in no way am I hinting that GTR is in the same brand segment but I would say GTR is another ground breaking icon as much as the NSX by HONDA).