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.
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.