People need to experiment more!
Now. When I say experiment. I mean, in a normal game with 4-5 friends. Not in ranked or even solo queue... unless you ask first. But, experiments are how we find out about OP things. Blue Ezreal. Annie support. ADC Leblanc (That was a thing around season 2). Things that we'd never even think about until that one dude tried out something and whoa, it worked.
With things as they are now, there are a TON of various things that could work. Things that wouldn't even be thought of a season or two ago. For instance. People did start using Jungle Akali around the start of season 6. And... it actually worked pretty well!
I just played a game in ARAM where I built Veigar with Protobelt, RoA, and Rylais. So, could it work if someone build jungle tank Veigar? Really think about it before you shoot it down instantly. His ganks would be awesome. He doesn't really need to build tons and tons of AP items since he gathers AP so quickly. And with Strength of the Ages and RoA, you could be surprisingly tanky and still do tons of damage. ...of course your clear would be pretty terrible and you're very very open to being invaded... but hey!
But yeah seriously. Try different things out. Jungle, top, support. ADC is... not...as open to experimentation nowadays. Around Season 2, people were using things like ADC Orianna and ADC Annie. So... yeah maybe ADC Kennen? ADC TF? Idk. Jungle Karma, that was a thing for a while around Season 4... or 5. Can't remember. And that was BEFORE she could use her healing snare on the monsters. Maybe now she'll even have a better time.
All I'm saying is, just try out different things. Get a bunch of friends and brainstorm. If you find something that works, post it on youtube, post it on reddit, show it off. If you feel like League of Legends is getting stale for you, maybe you could try and figure out a new meta.
You tell me. Should players try and look for a new Sleeper OP meta? Or just stick to the good ole reliable?
ADC -------------
Jungle---------------
Jungle ---------------
Support -----------------AP 
& thunderlords with extra pen masteries
support with
and AP items works well in most match ups. of course, if my duo bot gets on the thing.
with AP items can pack a punch if you know how to play the passive minigame. but sometimes you get wrecked by tank comps so its a 50/50 change of winning. its fun tho...
ADC can be very underwhelming for the enemy since you can fuck them up both from range and in melee. since most of her spells scale with missing or maximum health it still does quite a bit of magic damage. but you may end up fucked if the enemy can faceroll you or CC you.
in the jungle, i never expected that to become popular somehow. i used
back then. havent played him with 
AD, no one expects the E DPS coupled with
and
AP, 50/50 like K6, depends mostly in how the enemy builds, but a single combo can one shot squishies
AP, because why not.....most of it is doing damage with E and massive heals from Q.
makes you really hard to kill unless you're a fool and try to man up 1v5
AP, good old CC and nukes with W...i mostly see him full tank or with AD items. but it can still get the job done