The word “throwing” in low elos is the most subjective and most frequent word used. To people in those elos everything is seen as throwing especially if one of your temmates do not play the way you think one should play on that particular hero or role.
I’ve personally accused many ppl of feeding for example since I saw them going in alone, but after actually reviewing the replay codes, I saw that the enemy was down 2-3 and our Rein for example would push up and no one would push with him and I was like “again another Rein throwing”, but I failed at that time, during that game to look at the killfeed and to realize that we should have pushed in order to get the “clean up”, since 4 or 3 of the enemies were left and then in the replay I realized that the Rein was not throwing, but the rest of us were because we did not support him and we could have gotten a nice teamkill and/or stagger the opponents who were left alive and did not pull back. The way we played it we let them pull back without a scratch, let them regroup and out-ult us in the next fight.
That is only one example.
People throw the term throwing way too loosely these day, especially in low elo. “He picked Torb on attack, he is throwing”. “Our DPS are running Sym/Junk they are throwing”, etc.
A D.VA into a Zarya is not necessarily throwing per se, especially in low elo, where neither the D.Va nor the Zarya know how to properly play against the heroes they are strong against or heroes they are weak against, so it basically evens itself out.
I’ve seen Junks and Syms destroy enemy Pharas, and I’ve seen the opposite as well.
The term “throwing” means intentionally not playing the game. Sitting in spawn emoting, jumping off the map the whole game deliberately, deliberately spamming hello and not healing for example, or keeping DB on 1hp allies, etc. I agree that the term “throwing” gets a sort of an expansion in higher ranks, like not using Zen ult on purpose to counter Grav, etc. but even that is not reportable according to Blizzard definition. That is called soft throwing. Like everyone knows you are throwing, but you are actually not breaking any Blizzard rules. Not using ults when you should or when you are expected to use them is not throwing according to Blizzard.
That is why you have an insane amounts of “soft throwers” and they will rarely if ever be banned.