I certainly get what you’re saying OP, bronze can be very frustrating indeed, and as you and Ethernyet noticed there are an even increased amount of trolling, throwing, smurfing and general lack of game sense going on in bronze. I know what you mean as I started in high bronze and was as low as 1200 or something I think at some point.
Took a long way of improvement, but I did climb out of it first in silver, than in gold, plat after that, I did not get my rank instantly by placements. One advice I can give you is to concentrate yourself on one, two, maybe three heroes, preferrably in different categories, and improve your game positioning and avareness with them. Do not flex all the time to different roles you do not know how to play yet.
Choose your hero picks wisely. To climb,I think a good bet is taking a hero who has the potential of playmaking (plenty of heroes do that), for me, it was Rein, as I could fulfill my role of team protection and compensate both for me and the DPS in damage. Others will advice you on a DPS, and it is a perfectly viable route too. Boils down to your preferred gameplay choice.
It can take a long time, but it is possible to improve. It is, however, not as easy as some say, it depends on many different variables and strokes of wins or losses, but in the end you can improve your chances of winning by increasing your teams chances if you perform good.