Two reasons you are getting downvoted
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This topic has been covered numerous times on numerous boards. People tend to down vote repetitive threads.
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Your suggestion on fixing it is literally what Riot already does. It takes a number of games to get an accurate mmr. Thus, there is going to be some stomping.
However, I will offer a suggestion. Perhaps on account creation they can ask for experience level, if they don't already, and maybe filter a little that way. Of course that requires honesty on account creation and would only slightly fix the problem since eventually their mmr will provide that information.