I have been teaching English conversation to university freshmen for 20 years, and this is what I think.
1. Conversation is the one, absolute, essential skill.
Without conversation, there is no language acquisition. Without the interest and personal relevance of conversations, the other skills just don't stick. They are just short-lived chores that soon evaporate.
2. Conversation should be the goal.
Clear, confident speaking ability is the highest academic skill, not the lowest. A world expert who cannot express their expertise in conversational terms is useless.
3. Conversation is the engine of improvement.
With enough speaking a critical mass is reached. Listening, pronunciation, grammar, vocabulary (and life-changing confidence) likewise improve and a snowball effect begins.
4. EFL education has the wrong goal - grammar - because grammar is easy to test. The goal is to pass one last multiple-choice, grammar test. This may be a transparent method of selecting university students but it is poor English education.
5. The ultimate goal - and result - of a ten-year English education should be speaking ability. This book will show you how to get it.