If you did a simple search on modern roundabouts, you would get many results about how much safer they are than comparable signals.
Your third paragraph is basically arguing that requiring most drivers to slow to 15 or 20 mph at a modern roundabout is less safe that coming to a full stop?
It is impossible to prevent road users from making mistakes, but road design can reduce the likelihood that the outcomes of those mistakes are fatal or serious injury crashes.  Modern roundabouts virtually eliminate the possibility of a fatal collision. If the jeep driver had behaved this way approaching a stop sign or red light, all involved might have died.