It's made it a thousand times easier for fanfiction writers, such as myself, to create more realized, in depth stories.
Being the huge D&D enthusiast that I am, I find immense joy in creating my own original characters in some of my favorite video game universes, don't worry though, I've steered as far as possible from the ever so common "sexy, misunderstood, half-angel half-demon hybrid." (Honestly, that character is so, and I cannot stress the so in this sentence enough, so common.)
In the earlier days of League, we were given only the most basic of information about the locations and factions that made up Runeterra, as well as the cultures and people that made it, that every group could be summed up with three words or less. The Demacians were the "good guys" the Noxians were the "bad guys" everything was so clear cut and lacked any depth, making it near impossible to create an original character without them being the most boring one dimensional character ever written. This has changed a thousand times over, thanks to Riot's incredible writing and worldbuilding teams.
Now, we're given an in-depth, interactive map of Runeterra, with the names of the most famous capitols, to even the lowliest villages, as well as perfect descriptions of the cultures and people of each faction. We can now get a better idea of the average, every day life of a person from each faction. We're given entire stories worth of history, and multiple short stories that help even further to describe life on Runeterra.
I've created multiple characters already. A Demacian peasant boy, who, after discovering his magical talent, moves to Noxus after being promised safe haven and acceptance, while struggling to accept the brutality of the nation. A Zaunite girl who despises the technology that makes the city after witnessing her parents become little else but mindless machines due to the constant augmentations that they needed to in order to work, and now wishes only to sail across the seas. There are so many others that I've created, and it's all thanks to the wonderful writing of Riot. Without their worldbuilding, none of my creations would have been possible.