What's the deal with player selection in promos?

Firstly, I understand that everyone goes through the grind of leveling up in this game. I guess my issue is that I'm not entirely sure how players on this game are selected. So when something like this happens in the last game of my promos I can't help but wonder why the odds are so obviously stacked in one team's favor. I get stuck with last pick and support and we end up getting blown out. What bothers me is the obvious skill gap in some of these games. This one for example has a Bronze 3 player and someone who is still in their promos to be placed in a division.