How can we be expected to improve if we only ever play against oponenents of the same general skill?

I first started playing league about two months ago. When I first got into the game I had several friends who had already reached level 30. I ended up playing the majority of my games with all level 30's, and around level 14 I could hold my ground and even win lanes against 30's. As a result of this when I would take a break and go back and play a game at my own level, I would nearly always get fed, it felt too easy almost. Playing with level 30's since I started helped me progress far more than I ever would have, had I just jumped in the game with competition equally as clueless as I was. Watching, observing and adapting to more skilled players, in game is how I improved so much in such a small amount of time. But now that I've hit level 30 I feel as if my skill has flat-lined, I carry games now and then, but it's rare. I wish there was a way that I could get in games with players ranked much higher than me. I feel like if I could get into games with only platinum/diamond players then a similar effect might take place. Yeah it would probably be a little bit rough at first, but I'm confident I would eventually adapt to the play style of the higher elos, and potentially be able to carry most games sub platinum. This brings me to my point. I'm sure I'm not the only person who learns best from adaptation. So for people like me, how are we expected to improve our ability at the game, if we only ever get to compete against players in our general skill level?