Sounds awful, why would you restrain a festival to only one method of distribution? Cannes is certainly overrated but they focus on authors first and foremost, and that's what led them to their current position.
Content produced for streaming services can be radically different from traditional studio content. Rather than think of it as a restraint it would be a celebration of the difference compared to traditional content.
The "restriction" would allow for streaming only content to be on the forefront than be eclipsed by traditional media which still dominates the charts.
E3 decided that they wanted to be an industry only event and banned the general public and all but a handful of elite media companies. In reaction Penny-Arcade launched PAX as an E3 replacement for the general public, one that also focused more specifically on gaming than E3 had been. PAX was almost immediately a roaring success and E3 continued to slide into obscurity.
It will be interesting if we see a similar dynamic play out here, with say Netflix launching a Streaming Media Festival or something.
Electric cars are the future of transport. If Formula 1 wants to be irrelevant then so be it.
Carving out your niche doesn't make you irrelevant. F1 has plenty of petty rules, yet it's still damn profitable.
The hype surrounding Cannes was overrated anyways. France isn't even a major market to be making that kinds of demands.
I foresee a major festival/competition for Streaming only media attended by A-list celebrities in the future.