You know atmosphere is more densely packed at sea level than mountain high.
Yes, the question is why. That is what you continually fail to provide.
Gravity explains it as a force acting on all matter trying to make it go down.
That provides the necessary force to make the air a greater pressure as you go further down.
Your model of it just being the air magically pushing down doesn't.
This is the issue you continually fail to address.
There is absolutely no need for fictional gravity to be involved.
If you don't want to involve very real gravity, you need to have something else to take its place, and the air simply doesn't cut it.
Your gravity is said to be a pull from the centre of your Earth.
If this was the case then all your atmosphere would be as dense at the top because it would be all pulled down to the centre of mass, according to your set up.
Pure BS, as repeatedly explained.
Including by the simple graphic you seem to hate as it so clearly shows the problem with your model:
The air right at the top of the stack is just being pulled down by gravity, without anything above it.
However, when it falls down, it hits the air below. This means not only is the air below being pulled down by gravity, it is also being pushed down by the air above.
This layer in turn pushes down on the layer below with an even greater force.
For the simple case of the diagram, all the air above is pushing down with a force of F.
The middle layer transfers this force to the bottom, but also pushes down with its own weight of W. This means it pushes down on the bottom with a total force of F+W, the force due to the weight of air above pushing it down and the force due to gravity pulling it down.
All of this pushes down on the air below making the pressure greater below.
You can also understand it from the force balance.
The air is at a greater pressure below. This tries to push the air above up, due to the pressure gradient, but this is balanced out by the weight of that air above being pulled down by gravity.
This also matches the pressure gradient in a fluid.
For example, if you go ~ 10 m below the surface in water, you will have increased the pressure by roughly ~1 bar
That is because the density of water is roughly 1 000 kg/m^3.
So if you consider a 1 m^2 column of water, that is 10 m high, that has a total mass of ~10 000 kg. With g being ~ 10 m/s^2, this gives a weight/force of ~100 000 kg m/s^2 or ~100 000 N.
Thus the pressure due to this weight is ~ 100 kPa = 1 bar.
So gravity explained perfectly well why there is this pressure gradient.
Conversely your pure nonsense with no gravity and just magical air, can't explain it at all.
Again, turning the system sideways shows this.
If your nonsense was true, there would be sideways pressure gradients as well.
You need a force acting on each layer of air, separate from the air above and below, or you can't have a pressure gradient in a non-accelerating system.
And as I have told you before, you can even simulate gravity by an equivalent acceleration, and see the effects of this now horizontal pressure gradient, such as the buoyant force making a helium filled balloon move forwards in a vehicle which accelerates forwards, instead of more dense objects, which appear to accelerate backwards to an observer in the vehicle.
We won't get into your moon pulling the water up from Earth despite Earth supposedly being 4 times as big with 6 times more of your magical gravity.
Good, because you clearly don't understand that either.
The whole set up is nonsensical gobbledygook
Only for people like you, who want it to be fake so you can pretend your fantasy is correct.
For any honest, rational person, who honestly and rationally analyses, they find it makes perfect sense, and unlike your garbage, it actually explains what is observed in reality.