Really, the problem isn't scientific. Various sci-fi authors have created all kinds of "hyperspaces" with well-defined rules that would allow for almost any interpretation.

The problem is that it wrecks the drama. Why wasn't this idea used earlier? It's blindingly obvious, not a clever deduction, nor was this some sort of special circumstance (no slingshot around a black hole or some other very unusual thing, for instance). Why won't this be the solution to every battle in the future? Why bother with capital ships if they're so vulnerable to this simple attack? Is the Death Star even necessary if ships can be this powerful on their own? Why did the Rebellion wait so long to deploy this? They'd have been in a wildly better position if they evacuated that ship at the very beginning and used it; the same effect on the enemy, only they have more of their forces left. Why doesn't the Empire, sorry, "First Order" use this on the rebels, sorry, Legitimate Representatives of the Galactic Government Who Are Somehow Still The Rebels? (Although here we come up against the silliness of a sub-light stern chase being the whole movie in a universe with trivial FTL, too. The failures of this movie are like the Shrek onion.)

The problem isn't the science, and it isn't even necessarily that the questions are utterly unanswerable, or that if you try hard enough you can fanon the problem away. (Though IMHO in this particular situation, you must fanon very hard.) The problem is that it raised all these questions, and didn't even acknowledge them, let alone try to address them, and that smacks of bad writing.

There is this popular idea in the writing world that writing science fiction means you can just do whatever you want, whenever you want. The producers of Star Trek: Voyager, for instance, had this idea and clearly articulated it in interviews. And, well, in some sense it's true, but in the sense that it's true, it's no more true in science fiction than it is in any other medium. Nothing stopped Doyle from Sherlock solving all his mysteries by consulting a medium. Nothing stopped Rian Johnson from solving his problem with this particular ass-pull. But being science fiction doesn't prevent the same dramatic consequence happening to the latter as it would in the former. At best it just gives fans a few more avenues for fanon. But that's not good drama.

There are no stakes in a universe where anything can happen at any time.

In particular, I'd highlight that whole Empire/rebels thing again, because that's even more important than the scifi tech stuff. There's just no sensible grand-scale interpretation of the legitimate government of the galaxy being chased by some upstart First Order, and the First Order having all the advantages, literally all of them. (Some advantages, sure, especially around having Sith support. But when did the Galactic government get so anemic? We saw much more strength in tangential fights in the prequels.) Honestly the sequels have been screwed up from the getgo because the writers think they can just do whatever they want, whenever they want, and that the quality never suffers for it. They're spending against an account they don't even know exists and overdrew against it so hard that they may have actually spent Star Wars, Star Wars of all things, dry.