Actually, the use of "he" as a gender-unspecified pronoun does not work at all well. At best, it is ambiguous. In contrast to "mechanic...he", how many times have you seen "nurse...he"?
That's because the author assumes that nurses must be female, which is the author's issue to deal with. Being "ambiguous" is an important property because it allows the author to leave the gender of irrelevant actors as irrelevant. In the shopkeeper example, if it isn't important that the gender of the shopkeeper be known, why make it an issue by specifying it is a she?
In fact, one of the short stories I enjoyed the most recently didn't nail down the gender of the protagonist until halfway through, and it made me realize the assumptions I had been making that weren't correct and shouldn't have made. That was a good author, in my opinion.
For that matter, how about "mother...he"?
Well, now you've just used an inherently gender-specific noun with the wrong gender pronoun.
If you can't use "he" to refer to a role that's almost certainly female (not quite certain; a mother could get a sex-change operation), then it's not a very good gender-neutral pronoun, is it?
"Nurse" is a non-specific noun. "Mother" is much more specific, but true, a female mother could have a sex change and become a male mother. In fact, saying "mother ... he ..." says that's what has happened. You have a male mother. Otherwise you'd say "mother ... she ...". In this example, you don't want the genderless pronoun.
The fact that you can't read contemporary writing reflects a lot more on you than on the writing.
Where did you get the idea I cannot read contemporary writing? It's writing where the author has chosen to display ignorance of the language that causes problems. Any author who displays ignorance of the language he's using to craft his work causes awake readers problems.
Not just contemporary, by the way, since people have used "they" as singular gender-unspecified pronoun for quite a long time now.
Seeing "they" where it should be "he" or "she" isn't a serious problem, and I automatically assume that the author doesn't know his plural from a hole in the ground. ("They" always has been genderless.) I certainly don't wonder if there was something I missed about "the shopkeeper" when I later see him referred to as "they", because the singular and plural for "shopkeeper" are different. The author has a clear way of specifying a plural "shopkeeper" and did not, thus he is not. But when "the shopkeeper" is later "she", I do wonder why the specificity was necessary and did I miss something that would have announced it earlier. By using the specific gender pronoun "she", it is as if the author is creating a red herring in the plot-- something the author is saying is important to know that turns out not to be important at all because the character never appears again. That's the sign of a bad author. But using "she" everyplace that "he" should be used is the sign of an ignorant, arrogant author who wants to teach people a lesson about his incorrect belief in the sexism of language in a context where it is not relevant.