If you don't plan, the joke may be on you. Career plans were never set in stone. They always required revisiting on a regular basis. What is true is that the fine print on the plans have become very fuzzy as workplace endeavors are born and die from year to year. Many of the most practical plans are really big-picture glimpses of career mission concepts.
Details are sketchy or nonexistent.
But I argue that some kind of plan is essential. Start with an estimate of the normal progression in your industry or career field. Perhaps the standard is two years in technical training followed by two years of field experience. Maybe your typical path is five years in patrol followed by five years in investigative work. Possibly the timetable is eight to 10 years of work experience before moving from architect to senior architect.