I think some lessons can be learned from other sports and other countries. Who would think that Major League Soccer, in the United States, would be the 10th best attended soccer league in the world, with avereage crowds better than countries like Brazil and Japan where soccer is no. 1, and populations are huge.
About 10 years ago, the MLS had poor crowds and no interest, they brought in marquees like Beckham, etc, but found that it was basically a circus sideshow and didn't make long lasting fans. Their biggest positive is stadiums, their next move...
Most of the MLS clubs are owned by billionaires who built purpose built stadiums, ranging from 18K to 28K, (with the exception of LA Galaxay (Beckham) and maybe 1 or 2 others that play in larger stadiums.
What this does is create a scarcity. If you know you aren't guaranteed a ticket every game unless you become a member, you often won't become a member. If it looks like rain, you'll just say stuff it, i'll watch from home, and not buy a ticket to the game. If you're a ticketed member, you've already paid for your seat, you're more likely to attend. That way, you boost memberships, and you boost average crowds. The clubs benefit. Ratings benefit as it looks better on TV as well.
I think the NRL are very wrong with their "big stadium" push. You know you can get a ticket to a game at Allainz or ANZ whenever you want. Why get it in advance? And don't simply think of the population size of the US is the reason for bigger crowds. The US population spread is so much more diverse than us, we've got about 3/4 of our population in NSW and VIC and 3/4 of our teams in NSW. There's multiple 'derbies' every week in Sydney. MLS in the US has only 1 city with 2 teams (LA), and only this year will New York get a 2nd team.
Food for thought...