I would rather listen to Paul Carter (lifteunbang on IG) than Mentzer advice, if you want to maximise muscle gains. He promotes high intensity, low/ optimal volume, who seems to get it right.
High volume is wrong, but Mentzer was wrong too. The truth is somewhere in the middle.
4-6 hard sets per muscle group, to failure, per workout, twice weekly frequently will maximise muscle gains.
That’s like doing 2 exercises per muscle group, in a workout.
On a chest and shoulders workout, you’re doing 4-6 sets for chest and 4-6 sets for shoulder. A total of 8-12 sets total for a workout. That’s perfectly sustainable.
4 workouts per week is optimal, maybe 5 if you really love training. 3 if you’re doing for general health and maintenance.