Comprehension-driven language learning focuses on learning to process messages in the target language. The assumption is that speaking will eventually emerge on its own, and that pronunciation and real creative use of the language will be better if comprehension comes first and is emphasized more. Meaning is much more in focus than linguistic form.
Language acquisition is a developmental process.
You need lots of comprehensible input. Productive skills are harder than receptive skills. You can't rely on memorization alone. Memorized material can give a false impression of your proficiency. Your brain analyzes language whether you know it or not.