I play primarily Zen but often flex to whatever is needed. My career high is 3988 SR (1 game away from GM #feelsbad) What I found was diamond to low masters was very hard to climb on support unless I was duo queing with a DPS main but 3700 and up was very easy to climb. Once you get into upper masters everyone knows to follow up on big plays, peel for support, target prioritization etc. In low masters and diamond these things aren't always consistent so you can hit every game saving trans, discord all the right targets, win duels against flankers... and you team still will lose team fights somehow and lose the game.