I think Kogarah has to be seriously evaluated. If you got this crowd in a regional area it would be dire. Let alone in the middle of Sydney. The Saints are moving below Cronulla, especially with the Sharks ground capacity heading towards 18k soon. Kogarah might be worth 1 game a year for heritage round, but I don't see value in it with these sorts of crowds, form fully understood. Base line for an NRL team home ground should be 10k, ignoring form and opponent. You can't just turn up once every decade when the club is threatening to take games away and expect it to remain a regular NRL ground.
That or change your marketing towards your current demographics and not the the demographics you had 60 years ago. Marketing and community outreach have been dire for years, including through the premiership period around 2010.