You don't have to be fast enough to be a WC in your own right. You just have to be able to be up the near the front and in a position to be able to help with strategy. The perfect number 2 was Bottas at Mercedes. He was never going to win a title but was more often than not up the front and on occasion able to take advantage and win when Lewis didn't.
The help with strategy is overated. Max is helped by always being able to be on the right strategy for himself. All 3 of the other top teams are racing each other and taking points off each other. With Lando and Oscar they are racing each other into the first turn and always having to stop 1 car not on the optimal strategy as they are a lap late. It works perfectly for Max what they have, makes him look better when they are nowhere in the constructors as well, he would love it.