This is very true, Dale.
My horizontally polarized 6-fold Oblong has an extremely sharp null. I have used it on summits and in contests. You can blank out one very strong station, but when multiple big guns come in with their signals from different directions, it can be very disturbing.
For a Wednesday noontime SOTA activation with almost zero traffic, when I am desperately looking for any chaser available, the bidirectional antennas (single & double hourglass, oblongs…) are ideal for “both-sided fishing”.
For a very busy contest a Yagi is definitely a valuable add-on as shown in the very first picture in this thread.
73 Peter