Off the cuff, as a plat support main, here are a few quick things I spotted:
1.) You got paired with some awful teammates, more than 3 of them had a sub 30% winrate in ranked - matchmaking OP!
2.) Your first ranked game wasn't much of a game so much as a 20-minute blowout. You didn't really play.
3.) If you do well, you tend to do REALLY well. So I think you have good fundamentals based on that alone - You run into problems when you start falling behind, so I'd suggest you look at what you're doing during a game where things are going south.
You tend to die more in these scenarios and your KDA drops hugely. This suggests to me that you should pay more attention to who is fed, and watch out for fed opponents, and KNOW when you can't win.
This also suggests to me that you THINK you can kill people when you might not actually be able to, leading to unsafe or 'risky' play. Double check your engagements, ESPECIALLY when the enemy team has some kills.
Recovering a 'bad' game is incredibly difficult, and many times impossible, but that definitely seems to be where you should put your focus, I'd wager.