This problem isn't limited to 135. Part 91 can have the same problems and so can new 121 pilots. The root cause of the problem is training. The pilots in this mishap had over 15,000 hours between them, yet they could not identify their approach as unstable.
That's because CAE, Flight Safety, and the others don't really have a vested interest in your training. They don't care about your specific company procedures and cultures. They provide training for the checkride and nothing else. If your 135 or part 91 company actually has a true safety culture, then that's fine, but too many don't. Whenever something bad happened when I flew charter, the first question asked was, "Were their passengers on board?" They only care if passengers were on board and how the PASSENGERS perceived the event.
I worked with so many pilots that put passenger comfort over safety because of that culture. Some did know what an un-stabilized approach looked like, but few believed in actually going around for one. One of our most experienced pilots in our recurrent training class actually told our head of safety that he had different rejected takeoff criteria at non towered airports since there wasn't a controller who would report the incident. And before you say, "that was just your company" Most of the pilots flew at other 91 and 135 operators before and I flew with pilots from other operators in the sims.
A brand new 121 regional pilot is the same. The difference is 121 has a much more consistent training program and robust safety culture. While a new 121 pilot might not take un-stabilized approaches seriously at first, after 1 year they would have read numerous safety reports from their company chastising un-stabilized approaches to the point where peer pressure alone would make them change their mind.