Assuming a 'fair' network. In absence of Net Neutrality it was "Dear company X, you better pay us or your packets will be delayed/dropped and your customers unhappy", and " Dear customer Y, you better opt for extra service A,B,C,D, ... if you want to Game/VoiP/VoD/Chat ..." and very much worse.
"Private networks tend to make things worse by having fewer paths available increasing the average minimum distance."
This is not how internetwork routing works. Obviously a straight line darkfibre line from A to B will beat any route a generic Internet can come up with. It is not a case of Riot Direct xor 'the rest of the Internet', but selectively supplementing by deploying handover points at strategic peering locations in the internetworking fabric where things can have a large impact.
Having said that, I admit it’s not pure snake oil and provides minor benefits to their customers.
Cables aren't laid out straight, but network infrastructure adds a majority of the cross continental latency.
But gaming from the moon would not at all be feasible using light. I wonder how we could solve this for future space communications.
PS: LEO satellite constellations like Starlink have a lower theoretical latency around the world than fiber as the signals are traveling in space, but a longer path. Significantly beating that is going to require magic aka a useful fundamental change in the laws of physics as we know them.
In the end it’s just a question of where the servers are relative to you and nothing else really matters. Private networks tend to make things worse by having fewer paths available increasing the average minimum distance.