Slightly unpopular opinion: All official lore is crap and should be generally ignored. (Even the stuff I kind of like) If I want to play in a world where what I can do is limited by the generic, inoffensive, middle-of-the-road, crowd-pleasing writers at some corporation I’ll just play a AAA video game. The ability to be participatory in the creation and evolution of the in-game world is what makes TTRPGs different from consumer media. Why would you give that part up, but still leave yourself with all the cognitive load?

The point of having the system before you play is just letting everyone know what to expect on the G part of RPG so they can focus on the R and the P. It kills all momentum to stop and ask, ‘so what system do we want to use’ in the middle of the game. No system is perfect, but it cuts out a lot of work to just pick one and roll with it, homebrewing over the few holes that show up.