Someone training 4-6hrs/wk isn't going to benefit from periodization as much as a pro training 25-35hrs/wk. In fact, I would argue it would make them slower than just doing high-intensity (including anaerobic efforts) all the time. When you can recover from your workouts no matter how strenuous they are, there is little benefit from going "easy."
So typical periodization would involve building your CTL "base" with quality aerobic workouts. One would then increase intensity, which typically sees a drop in a person's CTL/weekly training hours in favor of building VO2/AWC. Tapering eventually leads to more CTL loss in favor of freshness.
For me, I can recover from 8-9hrs/wk of training, no matter how hard I go. For example, in Superweek, 16 days of mostly 75-90min crits (with a few 2-3hr road races) will not wear me out. I usually only start getting tired around my 9th hour of racing.
So, what is the advantage of periodizing my training plan through the winter if the hardest racing I will encounter are 75-90min of intensity, every day of the week, and I can still recover just fine?
At what point does periodizing your training program become, relatively, useless?