An easy way to get rid of smurfing is to implement this into the reporting system - if someone is identified as a smurf by 10 different players, then they get ranked up substantially and put back where they belong.
Deranking should be punished with a permanent ban on competitive playing (or a 3-month cooldown).
But the ranking system is too stingy with points - if you play top game and get all golds, it only takes 2 deranking games to more than undo that, so a user-driven smurf reporting system should skyrocket them to where they belong and then have normal ranking resume from there (for instance 10 smurf reports from 10 different accounts over 10 games and 30 days).
This may encourage deranking, and a confirmed deranker (which is easy to spot) should be given a 3 month cooldown period on competitive playing.
This type of system might stop people from smurfing or deranking since there would be no way to achieve this long-term.
unfortunately blizzard only cares about money, and keeping player numbers artificially high, so they wont do this…