"Plus, according to PBD, f/2.8 and f/4 look the same, why bother?"
And again you selectively misquote. F2.8 on a crop camera and f4 on a full frame camera when using an appropriate focal length to achieve the same framing don't "look the same", they are identical in dof characteristics. It is called equivalence. See my demo below.
You on the other hand have stated very vigorously that any photograph can be taken with any camera; when challenged you further stated, specifically, you could take any image including any image shot with a 135 @ f2 with a box brownie.
One of us can demonstrate our point with images, one of us keeps changing their position. Have fun Ramon, I am not interested.
I misquote? Lol, you said it yourself that one stop isn't an noticeable difference between f/2.8 & f/2... so F/2.8 and F/4? No real difference to PBD.
Below: Sure, a great shot with any camera, but it won't be convenient.