Well i just want to start first off by saying that the Symmetra isn’t technically smurfing.
I doubt the system Blizzard created that places you in the correct ranking after a long time of data collection can put them in the proper ranking after such short time.
And since the player is playing at their best, it’s at most an alternative account.
Since playing at his best will result in them getting into their actual ranking, which is actually allowed.
It’s also hard to manipulate MMR in Quick Play, it doesn’t change quickly and you don’t have any visual statistics to see where you are on the ladder within Quick Play.
Why would someone buy an Alt/Smurf account?
Well high ranked players face high queue times, of course that isn’t much fun if you want a quick competitive game.
Other issues could be present in high ranked games, we can take hero bans as a previous example since that made alt/smurf accounts increase drastically.
Some players buy a new account since they believe they aren’t in their actual ranking.
Those players usually get ranked above their main account, though tend to drop down where they actually were quite quickly.
Others like to have everything under control, same goes for cheaters.
It’s pretty much playing god, which honestly could be fun… but eventually becomes boring because there is no element of surprise anymore.
Well Blizzard doesn’t really ignore it.
It’s not easy to detect a smurf since you’d have to detect throwing.
Because the only part that isn’t allowed with smurfing is the part where they throw into a lower ranking, you can’t make an automatic ban system for this and it takes long to process a report.
Alternative accounts are completely allowed too, so nothing reportable with that too.
Quick Play is meant for quick matches, this means that the MMR isn’t super strict.
There isn’t much data on those new players, so even if you were to create a stricter MMR system these players would still be put in your matches.
Next to that Queue times could increase for QP, which honestly is the last thing we’d need.
Just note that smurfing / using alt accounts isn’t always for boosting their ego.
Creating a stereotype isn’t always going to do you good, even if it seems they are ruining your games.
And well, smurfing is reportable if you have proof of them throwing in that match.
If they are just playing good then there is no rule being broken, thus you are most likely filling the report system with reports that cannot even be actioned by Customer Support.
So i’d recommend only reporting when an actual rule is being broken, this way there is room for reports that can actually be actioned.
The issue is hard to fix without damaging the general playerbase.