When you hear people faster than you talk about their training, translate their workouts into efforts relative to race pace. A 20-miler with the last 8 miles at 5:00 per mile sounds really fast—and it is—but for an elite man, it’s a long run with the last portion at marathon race pace. That’s the sort of workout most people prepping for a marathon can and should do.
Focus on the general patterns and effort levels in others’ training, not the precise numbers that happen to coincide with those effort levels for a given person.