The template itself provides guidance and milestones so that you can measure your progress. If you are not achieving the results you want, you can revisit the template to check that you have not overlooked something or misinterpreted what is required.
Marketing plan templates are developed by people who have achieved success online. They capture the lessons the author has learned along the way and save you the time, cost and effort required to develop your own. Once you have mastered a particular marketing plan approach, you can then expand by refining the template you have used or by adopting another template that might be more suitable for the marketing of a different product or service.