What no one seems to understand or realise....
If you have limited support around breaking partnerships or taking "set" batsmen out, then obviously your average will be inflated because you'll be spending more time trying to get set batsmen out yourself and less time bowling at new batsmen. During his pomp McGrath could often go away after a spell knowing that a wicket would likely fall to one of many of the bowlers that played with him (MacGill, Warne, Gillespie as the main lights) - that would have lowered his average, it doesn't mean he's not a brilliant/superb bowler, but look at his wickets per test strike rate in comparison to Steyn or Hadlee, who have freakishly similar statistics.
McGrath took 87 tests at a time that Warne took 92 tests to get to 400 wickets. They often bowled in tandem and were great at ripping through sides.
Steyn and Hadlee took 80 tests, Steyn bowled less balls to 400 wickets than any other bowler and did this without ever having a world class spinner in his line up, nor the luxury of a lengthy period with someone like Gillespie - if Rabada had been around five years ago, then maybe you'd have a point in the line that he had good support but no other bowler was taking wickets at a rate of return that Steyn was for South Africa - if they had been, South Africa would have been dominant in almost all conditions considering their god tier batting line up when Graeme Smith, Jacque Kallis, ABDV and Hashim Amla were all together.
McGrath is easily in the top 10 pace bowlers of the modern era, but Steyn is probably #1.