The structure of Shute Shield is that there are a whole lot of (dedicated) social players still needing to be catered for. It's a great day out for friends, family and the die hard stalwarts. But ask anyone who doesn't have an abiding interest and it is seen as a high quality social sport.
It refuses, mostly due to it's cumbersome structure of 5+ teams, to change from traditional kick-off times. This completely excludes your major supporting base from ever turning out in sufficient numbers as they are all playing rugby at the same time. Just remember 3:00pm is kickoff for 40+ Subbies Clubs, AAGPS, CAS, ISA et al, meaning they can almost never make a game in person or watch it on TV.
The failed experiment of the ARC and the underwhelming NRC (due to lack of connection, not quality) were brought into existence because Shute Shield didn't grab the proverbial bull when they had the chance. Had they been willing to present themselves as a professional sport rather than a niche continuation of the Old Boys networks I doubt very much if Australian Rugby in general and Sydney Rugby in particular would be finding itself struggling as it does. Exhibit A - The removal of Penrith, Exhibit B - The sale of TG Milner.
Shute Shield easily has the quality to support itself as a professional competition. Sadly, it refuses to present itself as such. So those with the real money to put into the game at this level are unwilling because it looks like their money will be spent propping up 4th graders and 2nd grade Colts who will never draw a crowd large enough to justify the investment.