So how did VFR fly around above 5000’ at the same quadrantral levels as the IFR aircraft and not be a collision hazard ?
Because they obviously were a collision hazard, just as two IFRs still are and two VFRs still are under the hemispherical rule. It was mitigated by the VFRs practicing "see and avoid" (and the IFRs too if they were in VMC sharing the airspace with VFRs) which is what the system you desire so much depends on. If in IMC, well the IFRs shouldn't have had to worry about VFRs at their level should they? On top of that the IFRs got a directed traffic service about other known traffic. And people managed.This was in the supposed good old days of GA when the volume of traffic was higher. It didn't seem to cause too many problems.