Vs AI problems

Well, I've only ever played vs. ai easy on league of legends. I still struggle to do well, and I'm expected by the people I know who play the game, to go on ranked and do well.

So, I go to a match to try out my recently purchased Lucian, for the first time, and I end up with allied aatrox on 31/1/3, master yi on 22/3/1 and teemo on 30/3/3. This kind of thing has been happening all night. I'd like to ask, how come players who are either from high elo or good enough to play pvp and do astoundly well, come on vs. AI? And, as players, do you think there should be a limit on who can play vs. ai based on their previous match history?