The answer is Comp matters if people of the same skill level are playing against each other.
If it's a Plat playing a top Soraka vs Bronze, then no. It doesn't matter. The Soraka will 1v5 you. If it's a Plat Soraka top vs a Plat team, you might reconsider your pick.
What matters in an equal skill fight is mostly that all bases are covered: Have a front line, some sustain, and at least 1-2 players who can soak damage from full lethality or Mages.
Going 4 adcs in the current meta just doesn't work if they are all built adc. (I've built a tank MF on an adc team. That works).