thanks for balancing the underdog so well that if a fed team is winning really hard, and their opponents get one or 2 kills, they can overcome and become unbeatable just from those 2 kills and win by a landslide

i think what you're seeing is fed team stops paying attention, makes a bad play, loses team fight/momentum.
The lane phase is drastically different from the team fight phase now. I played a couple games where the carries who got their butts kicked went on to get the bonus gold of shutting down a few champs and it evened things out, which was the point. Past that, the team that fights better together, wins.