Thing is that both are orthogonal concepts. You can optimize a network for latency or for throughput. A network optimized for latency can still be net neutral in concept and intention. Even an under-provisioned network that tries to fairly deal with optimizing for both low volume low latency applications and high volume latency tolerant applications at the same time while filtering out bad actors can still be net neutral.

Riot has their own network because they want a different kind of optimization than the traditional ISPs and Internet backbone providers aim for.

Network Neutrality was born out of the observation that dominant (read quasi monopoly/duopoly) were actively undermining offers from 'over the top' (meaning offered over the 'generic' Internet service rather than packets over a dedicated managed service offering from the ISP, think Netflix vs your ISP's own VoD offering) service providers by selectively shaping the traffic to degrade their offers. At the time, services such as Skype (pre-Microsoft acquisition) were their primary target as they impinged on the juicy profits from both traditional PSTN and ISP owned VoiP offers (ISP and Telcos were/are pretty tight).

The history of telecommunications has been a perpetual battle to reign in rent seeking natural oligopolies. To pretend no active fairness policies are needed or desirable is denying the obvious.

This by no means negates that lively and continual debates on exactly how to translate policy intentions and objectives into a real network fabric aren't necessary, as fairness is an emergent property relying on very many different punctual choices in configuration and deployment, the impacts of which can be detrimental to the objective both by accident or through deliberate obfuscation.