When League of Legends players refer to meta, they’re talking about “the game within the game” – the common strategies used within the game.
There are lots of alternate “metas” – and what is old becomes new again (aggressive counter jungling from M5, double brusier bottom from Dignitas, etc). The problem is that none of us really do this for a living, as the other poster mentioned, but it goes further than that – if you’re on Reddit, reading this blog, or really interested in the game, you probably watch streamers a lot – which means you develop your meta and understanding based on what they do, and unfortunately deviations to that (especially at non-30 or low elo) are insulted/decried.
Great example – I love running AP Soraka mid and AD Kayle bottom. But try and do that in a smurf game/normals/lowish elo (I’m 1400) and expect olks to AFK/complain. For every game I’ve had someone go “awesome, I’ll try to pick a champ around that!” I get 5 more that dodge queue for it. But then pro players started running AP Soraka and AD Kayle – it became more accepted and okay. Rinse repeat – I have enough time on my hands that I can theorycraft and develop new strategies, but because I’m not famous, nothing I say matters.
Try running an Orianna/Soraka double mid or bottom sometime, and you’ll see what I mean, despite those two being ridiculous together.
We’re stifling innovation by only accepting change when it comes from our streamer gods. Non-pro players can, and do, come up with excellent strategies and meta-breaking ideas. You don’t need a pro player to tell you if your build, runes, or masteries are “right” – just practice it and try new things until it works. (I mistakenly used AD masteries on Sona and… well, I dominated that lane.)