Those who claim that the use of a secondary fermentation vessel to clear and age beer is out of date and more harmful than beneficial have yet to put forth any real scientific data supporting their thesis.
Nor have you supporting yours.
I do not have to prove my claim. There is ample peer reviewed scientific data available that shows that leaving beer with the trub is not beneficial to flavor. It is those who are making claims against this body of evidence that have to support their claim via peer reviewed data from scientifically-executed experiments.
If performed correctly, there is little to no oxygen pickup during racking. Dissolved CO2 is off-gassing during the racking operation. CO2 is heavier than air; hence, off-gassed CO2 forms a protective barrier between the surface of the green beer and the air in the secondary fermentation vessel. Additionally, any oxygen picked up during the transfer will be consumed by the yeast culture and used for respirative reproduction via a phenomenon known as diauxic shift. Oxidation really only becomes a problem when the yeast culture is in bad health or has been filtered out of the beer.
I don't see anyone claiming NOT using a secondary is beneficial, just that USING one doesn't seem to be beneficial either. You assume racking is done correctly which is not a safe assumption in my experience. you also assume that most brewers, especially new brewers, are able to accurately determine when their beer has reached final gravity, this is also not a safe assumption. The main reason I advise against transfer to secondary is because so many brewers complain about slow or stuck fermentation after racking to secondary on day 3 or 4 because the recipe and instructions said to do it. Combined with under pitching prematurely removing the beer from the YEAST cake (not so much the trub) tends to negatively impact a lot of brews. The protective blanket of co2 argument is not accurate as in a dynamic situation like racking there will be significant mixing of gases in the head space. and remember that often the yeast culture is in less than optimal health in a homebrew situation. Like so many things, we are working with sub optimal equipment, knowledge, and facilities in the homebrew world and we have to take that into account when deciding how we are going to brew and how we are going to advise new brewers with questions.
I am not trying to discourage you from contributing to this conversation because I think that your perspective is important but you can't assume optimal conditions and draw conclusions about best practices from that when the real world situation is not optimal.