I personally think the type of injury or concern plays a big part in the decision too.
Also, whether or not foul play was involved. But for this topic, let's assume it's just an unfortunate accident.
Whilst extremely painful, possibly career ending and ultimately sad no matter the player, if it's a broken leg or ruptured knee etc. then play doesn't necessarily need to stop unless there is a possibility that allowing play to continue will further escalate the problem (e.g. play remains around or comes back across the injured player and risks their wellbeing). Next play-the-ball or stoppage (knock-on, dead ball etc.), by all means stop play.
Head knocks are a totally different story though. The impact, the sound, the motionless player that quickly turned into convulsing on the ground all made it clear that it was incredibly serious.
People can die from collisions like that so absolutely stop play immediately - no question in my mind. I also think that's why the rules allow the referee to use such discretion.
Broncos or not, I have no problem with the stoppage and hope the referees don't get scared / bullied out of doing the right thing next time.