I don't see what it discounts. People have claimed that the MP4 has the new tire physics that are a major improvement over the old. The fact you're stating it's much easier to drive than the MX5 just shows how unrealistic the road physics are for the majority of the game. The MX5 does not drive like it's on ice in real life.
I've not driven the MP4 so I'm disqualified from making any comments on it. But the skeptic in me wonders if people are raving about it because it's that good, or just because it's so much better than the unrealistic cars they're normally driving in the game.
The ice comment may be a bit over the top, because in my experience you can get acclimated to the iracing driving model. My problem is I then can't drive any other game. Because if I load something else up, I immediately remember everything I hate about iRacing. Hopefully the new model does make everything much better.
I think the guy claimed the McLaren was a total death trap which is why Gutter is dismissing his opinion. I haven't driven it either, but by most accounts it's a pretty friendly drive. He also dropped this; "In short, if you’re a road racing fan, there is zero point in even trying iRacing." which is hilarious, and undermined everything else he wrote, much of which legit.
To me, iRacing, like every other racing sim, asks you to take the good with the bad. Nobody has even come remotely close to putting the whole package together.
In iRacing's case (beyond cost, beyond no AI, etc) is that dreaded lack of grip. It's certainly true, and goes all the way back to the origins of it's engine with GPL. It's not unpredictable, there just isn't a lot of it.
What it is however is the undisputed king of online racing. It's miles ahead of the pack. That's why you play it, and by and large it's pretty exceptional at it.
Of course it's fair to be critical of it's physics, but there are many sims that don't have the best physics... or the best ffb, or the best graphics, or the best online. Yes, physics are VERY important, but there just isn't room in this genre to be outright dismissive of any title because they come up short in one particular area. You'd be left with nothing.