It’s bad writing. If they wanted to discard something sacred, they could have taken something which was actually in the series and discarded _that_. They sort of did this by ruining Luke’s character, only to reverse it at the end and have him save the day anyway. Really, Luke’s characterization really follows the same pattern. He was strongly characterized in all the other Star Wars films. Then Last Jedi throws this out the window for no reason whatsoever. Then by the time you’ve accepted that he’s a loser now, he steps up and saves the day. All more or less within the blink of an eye.
They’re just setting up a subverting expectations for the sake of doing so. It’s terrible writing, and terrible storytelling.
This complaint about TLJ resonates the least with me, as a (super, at one time) fan from well before the prequels. The seeds of this later Luke and of the situation of the Jedi are there in the OT, and I’m not sure what else you do with hermit-Luke in the setting established for the new trilogy. Sticking with “he’s still a gung-ho hero” doesn’t break “routine” (Johnstone’s terminology) and wouldn’t be good storytelling, and the way in which the routine will be broken has already been hemmed in by choices in VII (he’s withdrawn from taking an active role in galactic politics). At least with this direction, there’s somewhere to go with the character, and conflict for his scenes that’s not a straight repeat of him and Yoda in Empire.
Of course, all this was thrown away in the next installment, so it turns out I'm the fool!