There are 2 things wrong with what you say:
1. You never proved mission board flipping was used by a small percentage of players, because you never said what percentage of players used the mission boards.
2. Your data-driven approach is flawed, because it cannot measure the players who stopped playing Elite Dangerous (partly) because the mission generation sucked (and they either didn't know about board flipping or didn't like doing it).
While those who only play ED rarely, or avoid the missions, due to the poor mission generation, will also be greatly undervalued by your data-driven approach.
It's a bit like a bad restaurant asking their clients to rate their food - only those who like the bad food will keep coming, and so the food rating won't reflect reality very well.
Excellent post. Repped.
It is the Tomato Metaphor made real.