Sorry i dont believe you without proof. I have bad experience with players saying something here when reality is different. I have been in bronze several times. I played in normal times usualy after work or whole days on weekends. Few seasons back number of leavers went down. Yes in very low bronze you can find more leavers but in normal bronze above 1000 its same as higher. I had multiple runs with different accounts and its usualy the same. Its definitely not as bad as people say. Human brain works in a way that you will remember bad thing and experience much more than good one. Just try what i said.
Do note about your every game in sample of idk 30 or 50 games and count leavers on your side. But do it right, count only leavers who gave you serious disadvantage and you lost because of them. I sometimes have people who leave mid game and they will come back after while, they are not affecting outcome most of the time. Sometimes you have game when enemy team pushed payload and you cant even taje first point. People fighting ech other in your team. If someone will leave ať this point it doesnt matter 99% because its loss anyway.
I am trying to say that leaver who will leave soon after start or mi game and never come back is kind of rare.
There is only one thing i can suggest to you. Be nice to others and keep team morale up so people will not tilt and leave.