Or at least find a way to increase player participation in the 3's bracket besides offering cosmetic rewards that less than 1% of the player base will ever earn?
If they want 3s and 5s participation to increase here's what they need to do:
2s: 50 conquest per win
3s: 180 conquest per win
5s: 400 conquest per win
It's about opportunity cost for most people. Why spend 10-20 minutes in a 3s or 5s match when I can spend 3 minutes in a 2s match and be capped in less than an hour?
And for people going beyond capping it's also "why should I spend 10-20 minutes in a 3s or 5 match to boost my rating when I can spend 3-5 minutes in a 2s match." So they also need to widen the gap of rating gains between 2s wins and 3s and 5s wins. The reward needs to match the time investment if you want participation to be evened out.
Finally, they need to do something about CC DRs. In 2s it's a minor annoyance. In 3s it can be quite annoying. In 5s it can be downright infuriating.