What can I do in my ranked games to win?

So basically if you look at my match history for ranked solo/duo games and scroll down you'll see a good amount of blue...and then it goes downhill and it goes the other way...I was doing super well and then i was one game away from plat promos. It happened twice that day..and then it started going downhill as you can see from the amount of red games that have been happening since then. The games most of the time go where I do super well or decent in bot lane and still end up losing. I usually play safe and don't really get caught out too much. My losses recently have been due to people getting caught out a lot and engaging needlessly even after me spam pinging them. I try to give tips on being safe, playing better, and etc. but they are usually ignored. I try to ward as much as I can whenever I can because sometimes warding results in deaths which is a big cause for support deaths. I also play utility supports. Another issue I've seen in my games is where the enemy team has the better team comp..not much I can do about that. What can I do? My recent games have been where more than one lane has fed or made numerous mistakes by overextending or getting caught out and us getting punished severely just because of that person. Is this game just based on luck where it's up to riot to pair you up with decent teammates? Or is it really not because it's my fault that I lost because I didn't do what was needed for us to win? Constructive criticism please