One thing that really helps is the competitiveness of international RU. The game itself at that level is almost designed to let teams who have no passing ability or decent backs to compete with teams with really fluent attacking teams. No tries in you? No problem, just kick to the corners and win penalties.
The difference in quality between the All Blacks backs and England's for example is not far off as big as between the Kangaroos and England. RU allows England to compete regardless. In RL you cannot starve the opposition of the ball, or score enough points from kicks to win games. Our game rewards teams that move the ball around and aim to score tries. That's why most of us like it, but it does mean that gaps in quality get ruthlessly exposed, and I'm not sure there's any way to artificially close the gap even if everyone wanted to.
The way RU treats internationals as events is a huge difference. Forget the game and the score, its an event. Too many RL fans and pundits obsess about the game itself, and frankly make the whole thing sound boring. When minnows get smashed at the RL world cup, its all about what a joke it is and how fewer teams should be allowed in. When the same happens in RU its all about plucky underdogs doing their best.
RU fans also seemingly care far less about notions of 'purity' when it comes to international teams - the hysteria of some RL fans is unbelievable when someone could be selected to play for England under exactly the same rules used in RU, whether it be residency or grandparents.