I think the broader problem with super round in Melbourne is that it has largely been half-arsed and never really given a chance to succeed. With the first iteration having been this 3 year bloc sold on an ad hoc basis by the kiwi teams without really engaging the Rebels, the actual team based in the city they wanted to host it in, and all promotional responsibilities falling to a 3rd party there has never been a hell of a lot of vision or 'juice' behind it. Travelling numbers have been limited in no small part because there was little to no benefit in it for teams to invest in getting their fans there. The kiwi teams themselves seemed to be more interested in engaging there latent fan base in Melbourne and from what I've heard there wasn't even capacity for the other teams to be selling their merch at the venue. Why TEG didn't go harder on the promo I don't know. Possibly the deal they did meant the didn't need massive ticket sales to make money, they thought they could drive local ticket sales to hit their mark cheaper, or they just overestimated the desire of fans to travel and thought they could "Field of Dreams" it.
Going forward it needs to be managed by the Super Rugby commission itself, run with the engagement of all the teams, in a way where they actually stand to benefit. They may also mean taking a lesser bid from a host government intially, knowing that the city itself will be easier to engage and build the 'brand' of Super Round up into something people are interested in. That said, I don't think there's necesserily anything wrong with Melbourne as a host city, but people were never just going to turn up, not without significant prompting. That's meant lacklustre crowds each year have made it less appealing for interested fans to travel to the next. The way interested dropped off in my membership group over the 3 years was stark, and this is at a time when we had more people interested in Reds tickets year on year.
Properly engage the clubs and they'll engage their fans to bring them to the host city. Certainly there is appetite for teams to be organising these sort trips - the Reds have organised a charter flight and planned trip via their sponsor Alliance for the Crusaders game and sold it out in less than 24 hours of posting it to their socials.