Idiomatic code is useful when it is intuitively understood by someone not as firm in a programing language. Otherwise, it might become a boomerang,

That's a crock! No idiom -- and especially not the one you railed against -- would take any half competent programmer (in any language) more than 5 minutes to understand; even if they have to look up the documentation. (Woe & shucks; the idea that a maintenance programmer might actually have to reference the documentation.)

Heck! It probably wouldn't take more than 15 minutes to post the code here and get a bunch of replies explaining chapter and verse.

Only if a resource usage bottle-neck is significantly shown in benchmarks...

And that is the biggest fallacy of all.

Billions of pounds/dollars/sheckles have, and continue to be, wasted in government, defense and private enterprises, as entire projects and all the resources they've consumed, are scrapped; because performance was left as an afterthought and by the time it was considered, it was simply too late to restructure and recode the projects sufficiently to address the problem.

There has, to my knowledge, only ever been one project that ran too fast; a software emulator that ran DOS era games under Windows on Pentiums, that ran so quickly, the games as originally coded, became unplayable.

Every other project I have ever been involved in, be they on mainframes, minis, PCs or servers, be they processor-bound or IO-bound, batch or interactive, stand-alone or client server; I've never heard the users say: "Oh, could you make it run more slowly please". Whereas the opposite of that has, and continues to be, de rigueur across the 35+ years I've been programming commercially.

The practice of first world programmers, valuing their time over that of their users; their convenience over that of their users; their programming quirks, affectations and dogmas over the efficiency of the code they produce, and the productivity of their users; is the height of arrogance, and a primary driver behind the rise of outsourcing to third-world coders.