You need all of the ingredients to achieve your best.
Endurance, speed, strength, nutrition, race savvy.
Having a great kick isn't doing much of you're only kicking from 100th place to 90th place. You still need the engine to get you to the finish in the front.
Working on your speed doesn't take as much time as the actual distance running.
And all you coaches, no matter what approach you take your group may quit for a variety of reasons. And let's be real, distance running isn't the most exciting sport. Especially considering all the training it takes to be competitive.