I've never thought ranked was "only for competent skilled players," rather a way to see how you match up against other players. If you don't know the basic mechanics of the game, you won't get very far. And that's their own problem to worry about.
Also, number of wins means almost nothing. You can play 500 games without understanding everything about LoL and still end up with over 200 wins. Then play 300 draft pick and win 100. Winning doesn't make you understand the game better, it just means you've played a lot of games.
The current requirement is to be level 30, and people complain that you shouldn't do ranked right at 30. Make the requirement 100 draft wins, and people will complain about people playing right after getting 100 wins. Whatever the requirement is, others will get mad at you for not doing more than that. If fresh 30s want to ranked, they can do ranked, that's how it is set up. If they want to do well in ranked, then that's another issue, and one for them to worry about, not you or anyone else. "but what if they're in my game" then you try to help them (without being rude), and, win or lose, keep playing. if you're good, then one loss won't matter a whole lot.
"Weed out the noobs" is bronze, silver, up to wherever the person reading this is (because "everyone not as good as me is trash" in this community)