There's lots of weird stuff going on here. For the opening few mins of the game, you don't actually have any of your teammates in your aura, and when you do, you're on speed 100% of the time. I know you're trying to boop someone off the bridge but you can do that and provide some value for your team. It's also so blatantly obvious what you're trying to do that I'm shocked you got the Cass at all. You should have been killed multiple times during the first two mins of the game. Almost every amp is wasted and used without a real reason, you should be saving it and having a justifiable reason to use it every time.

By the time you actually get beat, every character in the game has already farmed and used their ult, with a couple of characters 50% towards their next one. Good beat usage is probably the #1 thing that is going to help you climb on Lucio and you should have had it way earlier if you just played on the wall above your team on healing aura at the start. When you do get beat, you position yourself in front of all of your team mates, in front of your tank's shield and get killed during it. It's quite possibly the only way for you to actually not win this game on the spot and you somehow managed to do it.

Honestly the stuff in the first few mins is so blatantly not what you should be doing, I'm completely unsurprised that your team flamed you. Reddit Lucio will help your team indirectly but you have to be getting lots of value out of doing it and not dying often, and even then, you have to farm beat and use it at the right times, and also be occasionally amping heal/speed for the team before you go off and do something else.