Nope, wrong. Catching standards have dropped dramatically in recent times, even Richie Benaud thinks that. I'd imagine many others would do too, if the matter came up in question.
In any case, there are always players who'll have far more fortune than others. Sehwag is one.
But then again, you basically refuse to accept that dropped catches even happen when assessing batsmen, so there's little point trying to detail these things.
See, no-one puts his success down exclusively to luck. Sehwag has had far more good fortune than most players, but he's still played plenty of fine innings and is still a good batsman - even as an opener.
I don't believe he'd be much cop as an opener against good seam-bowling on helpful surfaces and good catching, and on the tiny number of occasions he's faced such a thing he's come-up woefully short.
But he has played plenty of good innings, and even his first-chance average as an opener I'd imagine would be about 40, which is far from poor at all.
However, Sehwag's achievements aren't "extraordinary" IMO, not at all. Though some of his innings have been. Like Vivian Richards, Shivnarine Chanderpaul and a few others, his best innings' really are beyond the pale of what near enough anyone else ever to pick-up a bat would be capable of.