Been playing League for almost 10 years and seeing the lore and characters come to life is such a wonderful treat.
The animation style they used in this is great, it has a mix of 3D and 2D styles (spider-verse like animation but more defined), also giving you a kind of mature feeling when you watch it. The voice actors and the music (most of it was also produced by Riot) are definitely good and the story is written well, based on the real character's lore.
I would recommend you watch this if you are a League player because you would easily connect and understand the story and where it is going, but if you are not, watch it with an open mind at least, give it a try. Well, if you hate League for some reason, I do not expect so much for you to like it.