If you refuse to believe it then my 10 years of making fast-paced shooters won't change your mind. League uses a userland-level anti-cheat that is easily broken. This is why most of their hacking detection is server-side. Also, reaction time doesn't really play a huge factor in League. So as long as it's within human range, the cheaters can go undetected since Rio believes that using cheats to get you high human reactions "defeats the purpose of cheating." as documented here: https://www.leagueoflegends.com/en-us/news/dev/dev-anti-cheat-in-lol-more/

So overall, shooters are much faster and require client-side authority to feel good. In league, the game is slow enough to wait for the server to tell you what happened. In something like Overwatch, the clients report what happened. When you have that level of fidelity you need that level of trust. But you don't care about shooters, so don't worry about it. You can make your flawed argument that all games can be league and all anti-cheat systems can focus on league-like gameplay.