You are probably still playing with a mixture of former plats and legit silvers right now due to the reset. It isnt too uncommon to have last year diamonds laning vs last year silvers on my team.... while I am hopelessly watching from the support position.
I too am having more trouble in low gold despite getting 2 accounts in the top 7% last season. I feel like this is the nature of my two favorite roles though. Playing team dependent champions will require us to grind about 10x the normal amount of games necessary to climb.
I really miss the top 7% currently... The ADC's I play with now dont know when to recall, how not to overstay, when to catch waves in side lanes, stay out of the danger zones vs hook champions (like backing away entirely when nautilus starts walking past your caster minions), and many many more. I find it infinitely more difficult to carry silver/gold elo with top tanks or enchanter supports. Plat is wayyyyyy easier. Gold and under is easier to carry on carry champions though.