The gold system is what makes this game toxic.
Ok, before all, this is just my opinion.
I think that one of the sources of toxicity in most MOBA games is the gold "get money for killing and buy a lot of items" system.
This is the core of getting fed or feeding and this creates an advantange for the one getting fed thus giving a BIG disadvantage to the player who is low on gold therefore has less items and less power to battle the enemy.
Feeding (A.K.A. Giving money to the enemy) is one of the main reasons of toxic behaviour, generating insults and rage. Also its not fun when the enemy is insanely fed, because when that happens we hardly can win over the enemy.
But what if the gold system was changed or reworked?. what if you don't need to kill at all to gain any money thus not requiring it to buy items?
This will erradicate the "Feed or get Fed" problem and leaving players to battle with only their individual skill without any advantages nor disadvantages, not worrying for anyone to get an advantage (not taking in consideration general balance).
A good gold system would be something like the one on "Nexus Siege" game mode but at a slower pace, passively generating gold without the necessity to get kills or CS, and giving everyone the same amount of gold so there are no advantages or disadvantages leaving the game only to personal skill (and game balance but thats another problem).
Or maybe implement another system for the acquisition of item that doesn't involves "getting fed".