While i agree that EU airports are very efficient, 20 minutes before schedule take-off must be impossible. Surely you mean 20 minutes before boarding starts?
No, I'm usually the last person to board. Departure (but not arrival) frequently gets pushed back by 10-20 minutes, though I am making it on time even if not. I have literally never waited at a security check and it takes a minute or two to get through - speaking about EU flights.
There's no way you are not missing flights if you think you can get through security and to your gate regularly in 20 minutes.
Roughly every fifth flight they call my name, but I never missed a flight because of late arrival.
Do you only fly through small airports? I can't see how you would possibly guarantee not getting stuck in security at least sometimes
90% yes. I don't live nor work in the major hubs, sometimes I fly through as a stopover though (in EU you don't need to go through security again). I do this on purpose - often there are several airports about the same distance from my destination, so I just pick the least used one.