there is no fallacy whatsoever. I zoomed in to the image you posted it is still readable though not pretty but you completely missed the point. lets say we go to 600ppi there will be a uncomfortably small text size where even 600ppi suffers the same fate correct? so since you have already agree that a text size of <1 mm is daft what use is an even smaller achievable text size. you say diagrams, but surely they can scale too and they do. so at the end of the day it's about the pixel size being below a threshold and as I clearly stated "IMO" that threshold has already been passed to be of any practical use. what I would rather have is larger size and higher resolution not just dpi, it can remain the same or even reduce a little for all I care.

I know the internet loves car analogies so I'll give one, it's like complaining about the top speed of a good car, say a ferrari because there is a veyron yet you have a top speed limit of 70mph anyway. completely irrational IMO. The chase for higher ppi is exactly that, a chase for a higher number with no practical purpose. increase screen size and resolution, fine, but to aim for higher ppi to me seems daft.