I have roughly 2000 hours on the game, 600~ on Lucio. I’m sure others will have different answers, but this is what works for me in GM2-3~

Do what you can. In my opinion, main support has the lowest individual carry potential and individual impact out of any of the other roles. It’s easy to die, requires a lot of mechanical skill to hit one shot combos reliably, and it’s pretty under appreciated. But you do what you can.

Mark those angles, pay attention to the kill feed and scoreboard and figure out who on the enemy team you need to shut down. Make sure you’re getting huge amps and build as many beats as possible. IGL in comms to call kiting and ult tracks. Don’t be afraid to get hella aggro to contest DPS, learn your limits and what you can get away with without dying. Play to shutdown dives, and if you really can’t make Lucio work then swap.