What you say is true, but the flip side is that scientific research on programming language effectiveness is a very small field, and it's unlikely the academia

What you say is true, but the flip side is that scientific research on programming language effectiveness is a very small field, and it's unlikely the academia will be able to do the large scale studies that are necessary to establish meaningful results. (For example, no sizeable project is going to be built in two different languages just to gather evidence for a research study.) Without rigorous evidence we're left to argue from theoretical models / principles and anecdotal data. This is still useful. It would certainly be more useful to have rigorous empirical results to back up the claims and validate the models but we, as practitioners, have to make decisions on language choice now using the available resources.