Instead of just running A versus incremental-change A2, also run a B version that's radically different from A. It's like Google testing 40-odd shades of blue

Instead of just running A versus incremental-change A2, also run a B version that's radically different from A. It's like Google testing 40-odd shades of blue to see which performs better, while failing to discover that the best color to use is (say) red.