I believe that smurfing is a horrible thing, and it hurts the game in many ways. The existence of smurfs have turned ranked into a game of luck whether or not you have the smurf or are against a smurf. Beyond this, smurfing is especially dangerous for players in promos to an upper division or worse, rank. You can definitely be totally original and say "git gud" or "Yur just bad" but it doesn't negate the true existence of the problem here.
Before you insta-downvote this post because of the thought in your mind that rules against smurfing is impossible, hear out my proposition first. I am not making this post just to bash smurfs and not provide a solution, that would be dumb. Here is my proposed solution (Please revise it or correct it however you may see fit):
When an account is performing exceedingly well, like for example this smurfs match history ->(WilliamSail)<-, a system can then detect the account may be a smurf/booster, and then warn the player. Here's where my proposition gets iffy, because I know this may be way overboard. The system would then either lock the player from ranked or something less severe, and prompt this user to go to a link which would allow riot to verify if the account is the only account on the IP from the user (Very easy to do). From there, either an automated system or rioteers can verify whether or not the account is a smurf by searching accounts on that IP address, and if it is (if the player has a much higher ranked account on the same IP) then that smurf account would be locked out of ranked permanently, unless appealed. This is NOT a perfect fix, and I know there are probably better ideas on how to halt smurfing out there, but this is my suggestion. Smurfing and boosting is a huge problem for almost all elos, and a system to prevent players from doing this is pretty necessary. thanks for reading.