AWTA. Forget comparing averages, the current lots hits fewer tons and there are fewer players who are capable of going past 1000+ in a season. The current back-ups just don't score as many runs as the back-up we saw in the 90's/00's, it's really that simple.
Siddons is a great example; in any other time, he'd have played 50+ Tests and would have been a massive boost whenever Australia went to India. Imagine if he was 25 now.