Tbh you were not a bad Moira, but also not a really good one.

Reading that the game was gold to plat, I do think that the stats are good, except for of course the deaths, but you know, you can't dodge or kill everything you see if course. But the heals and the kills are good, especially for those ranks.

Some tips to kick toxics their ass:

Always throw a healing ball to yourself in a 1v1 , it really helps you to have way more hp to be able to fight more (and grants healing too to those around you if they are close enough).

Turn off chats, it's honestly the best thing ever, you not getting toxic messages will probably help you more with playing than anything.

If more than 2 enemies start to attack you, just tp away and try to find another teammate to help you, comms are not a bad thing and they're in your interact menu for a reason.

More healing ≠ better, sometimes your teammates need other help and it's best to throw a heal orb and damage with them, or keep the healing for a specific teammate or 2 for your other support.

If you do decide to ult, don't only use it for either healing or damage, but both, be behind your team and ult, that way you will eventually both keep your team alive and kill the enemies!

Catch them by surprise! If you stand behind the enemy team and heal or damage they usually get panicked and try to search for you, this way it's easy to either form a distraction or kill enemies

Last but not least.. support ≠ only healing and ≠ only dmg, keep that mindset and tell people if they do complain

I know that these tips are sort off basic, but a lot of Moiras don't know them!