Once or twice a year, I ll go back home to my small hometown in the lovely South of Germany and throw in a few workouts in the gym where I started out. And every time, I feel like I am in a time capsule: The same people doing the same workouts, looking the same ( while often wearing the same clothes).

What is amiss? How come most trainees do not make an ounce of progress on a year to year basis?

There are obviously too many variables at play to give a short answer but one common denominator  would be that most people move weights instead of training their muscles.
Yes, most trainees do the exercises, often with a good amount of weight on the bar but the actual work is done by joints, ligaments, inertia…in short everything but the target muscle.
An extreme example would be the guy who seems to be entering the “how low can I go contest” when curling a barbell. He might be “curling 60 lbs, but his biceps only move around 30 lbs whereas his elbows get hit with 100+lbs. Result: a blown out elbow and no growth.

It is a fact: when it comes to sculpting a physique muscle activation matters most.

Most people treat their training like homework, checking off a box 3×10 reps, all very neat and tidy.
Here is the issue: your muscles do not have eyes, they have no concept as to how many sets you did, what day of the week it is.
They only register one thing: How many fibers have been activated for how long?
The amount of fibers that have been properly activated per set is the single biggest factor toward your success in building a physique. It  will absolutely make our break your progress .

You know what the difference between me and a pro athlete/ bodybuilder  is? No, I do not mean the drugs is his ability to activate more muscle fibers during each set of training than you and I could ever dream of.  In numbers, pros use about 30 % of their fibers during each set. Normal mortals are around 8-10% that means that the pros workouts is three times as effective as ours.

If you multiply that by 100s of workouts over the course of years, it becomes evident why they look they way we dream of.

Well this sucks, thanks for nothing Maik. Have a nice life.
How about I ll show you a way to get at least halfway there?
How so?
It all starts at the beginning, the beginning of each rep that is.

Whenever you are starting a movement to flex a muscle, the body registers your intent and nothing else.
What does this mean?
The body will always use whatever muscle you activate first in order to move the weight. The first motion will more or less dictate the quality of the ensuing set.
Therefore, you must make certain that you are using the muscle you are trying to work, not just move the weight. This will also require you to leave your ego at the gym check in, but after all you are a physique athlete not a weightlifter.
In order to make all this a tad more practical I listed some pointers for each muscle that have worked well for me in the past ( by no means am I an authority, but you are reading this on your own free will so there).

When doing any type of pull always pull from the elbows, not the wrist. This will ensure you are using the lats first, biceps second.  Try having a light grip, do not make the exercise into a heavy biceps curl.
Two things matter most when pressing: 1. you must have an inward intention, which means that you should do not push the bar straight up but try to bend it together. 2. Try to imagine that  you are pushing yourself into the bench and the weight goes up as a result of it. Both of these pointers will help you avoid shoulder recruitment.
Shoulders (front part):
See above: when doing overhead press, always intend to bring the elbows together.
When working on your medial or posterior delts, you should have the elbows lead the motion, not the hands. This will minimize trap involvement.
When curling keep your wrist neutral and wrap the thumb under the bar. Secondly, try to snap the bar in half when using a barbell.
Put the elbow slightly behind the body in order to assure a maximum stretch.
Push your hips downward when doing hamstring curls. If you are using the leg press for single leg press, have a downward intention as if trying to slide the heel off the machine to ensure maximum hamstring engagement.
Do not change the angle in your knees during calf raises, otherwise they become mini squats.
There you have it, simple tricks to make your workout better!