So in other words, the strokes in question were not bad at all, and were in fact shots that ANY batsman would have played, even the best batsmen in the world, and were instead caused by good, consistent, accurate bowling and subtle movement in the air and off the wicket, as well as variation in length and pace. The fact is, if a bowler relies on poor strokes to get their wickets, good batsmen will cut them to shreds by avoiding playing said poor strokes. McGrath has been the most successful seamer in the world since 2000 not by playing against Bangladesh and Zimbabwe, but by dominating every single batting lineup he has faced, including the likes of Lara, Tendulkar, Dravid, Kallis and so on. These are not players who flail at average bowling and give their wickets away.
Like what? Get thrashed all over the park? This is honestly equivalent to claiming that Andrew Symonds is a more lethal bowler on a Kandy dustbowl than Murali. It's not just wrong, it's completely insane.
Hell, forget New Zealand at Adelaide, I could give you a dozen other games to look at. As I said earlier, the Adelaide performance was practically a McGrath trademark, taking wickets on surfaces where other bowlers cannot is what he does better than anyone else in the world. That's what is so utterly bizarre about your argument - if you were claiming McGrath was an overrated bowler on dangerous, seaming, uneven decks you may well have an argument as there are plenty of bowlers I would rather have bowling for me on those sorts of wickets. But, just like Curtley Ambrose was perhaps second to none in the 90s on a Perth or Bridgetown minefield, McGrath is in a class of his own on a flat, lifeless deck.