In reality drivers rely on models and predictions of other road users' behavior, and are committed by inertia to a course which requires those predictions to be true. We can tolerate more or less uncertainty, bigger or smaller margins, but a speed so slow that you can be sure of stopping in time for the most unlikely development right in front of you, is also a speed which is pretty much useless for transportation. The need to take this risk in order to go about your life is built into the whole system of urban planning and not something for which a particular driver is blameworthy. A driver becomes blameworthy to the extent that their tolerances were unusually tight for the situation. But even loose tolerances are exceeded some of the time.
I'm mainly reasoning back from the fact that drivers are causing so many premature deaths, yes. "If you're killing this many people then you must be being reckless", but I think that's sound logic? But also if we look at things like e.g. compliance with relevant laws, that seems to suggest that drivers are reckless as a matter of course - drivers flout speed limits all the time, to the point that they will often try to argue that this crime is somehow a non-crime because everyone does it.
One reason dashcams are so popular is people like to exploit the insurance presumption of guilt towards the rear-ender by getting in front someone and then slamming the brakes. Video which shows the scammer acting unreasonably to put themselves in the way can turn the tables.
Nothing about “accident” implies lack of culpability. By your and other’s logic, essentially nothing can be an accident as ultimately almost everything is cause and effect. Your dropping the milk on the floor wasn’t an “accident”, it was the effect of you not paying attention to the task of carrying the milk carton and being reckless about it (as an example).
If you were exercising reasonable caution when carrying the milk, it was probably an accident. If you were being reckless, then it wasn't.
The fact that drivers are such an overwhelmingly disproportionate cause of premature death suggests that they do not generally exercise the kind of reasonable caution that we'd expect decent people to use in everyday life.
The vast majority of collisions are caused by driver recklessness. (Yes, a few are caused by mechanical issues etc. as you say - but driver recklessness (e.g. speeding) is the biggest factor). Calling it an "accident" does kind of diminish their culpability.