Workout plans that have you ride 3/4 or 5 times a week with no workouts longer than 1 hour.
I suspect many use zwift for less than an hour at a time due to childcare or other commitments and want a structured workout plan. But all of the intermediate/advanced plans have you in your garage for 1 1/2 hours+. Build a plan that works on the little and often approach rather than long workouts that frankly scare people off.