Drill is underutilized only because it is boring to the teacher. But it is not boring to the computer. Entertainment and education should be the same thing. The only instruction that is boring is bad instruction. There are no uninteresting topics, only uninspired teachers or uninterested students.
All students can learn.
Given experiences to learn from, students can't help but learn. This is not to say that all human central nervous systems are identical. Some students form stimulus-response connections faster than other. Some students are more curious, creative, or motivated. Learning technology can provide instruction in such a way that each individual learns at his own optimal rate.