Note: I'm in the US, so my left lane is for passing, my right lane is for cruising/exiting. If you drive in another country, your sides may vary.

If your recommendation is that everyone travel at the same rate in all lanes of traffic, creating a rolling checkerboard pattern, I wish you luck. I predict that we won't see this behavior until humans don't drive the cars anymore. The closest thing in real life, with human drivers of all temperaments and motivations, is a traffic jam. If even one person wants or needs to travel more rapidly (or more slowly) than the mesh, the clash of priorities, expectations, and behaviors can create a dangerous situation.

If we assume that human drivers are not uniform in needs, motivations, skills, and equipment, then we can assume that their desired speeds may vary. In this circumstance, we should arrange the rules of the road such that all drivers are predictable and can navigate the roadway in a safe and efficient manner. So far, this is done by telling slow traffic to stay right, unless they must change left to pass someone slower* . Exits are typically on the right, so the slow can always transact with exits without having to change lanes. If someone fast wants to exit, they simply match speed with the right lane, change right, and exit. Everyone is predictable, Everyone knows what to expect from everyone else, and as such hazards are sparse. Imagine a sand dune on a treadmill in a heavy wind. The bulk of the sand moves steadily along (bottom of dune = right lane), but the grains that want to move faster due to wind (top of dune = left lane) bypass the glut and blow over the top of it. This evens out the dune into a flatter hill, then into a long, low rise. The dune treadmill can fit into a smaller tunnel after a long time of faster grains passing the slower grains. As grains pass, they recycle down to allow faster grains to pass. This theory should allow for the most efficient flow of traffic in a multilane system.

In such a system, if you have a car going slowly in the middle or left lane, the system becomes less predictable. The faster cars have to slow to avoid them, and may not be able to change left to pass due to faster cars. If there's room, they can pass right, but that's not a common situation, it's not what people expect, and it's therefore risky. This obstruction has the effect of slowing down the entire system, creating a rolling road block, and eventually a traffic jam as everyone following has to react to the obstruction and find a way around it. Hazards are high in such a situation. Traffic can't flow like water around the obstruction. One driver has made the roadway less safe and efficient for all.

I'm not interested in downvoting you, this is good discussion. However, although maximum throughput is theoretically achieved when all cars are uniformly traveling at a high rate of speed in a mesh, there are several factors that cause this to be an untenable ruleset right now. If someone on the left has to exit, problems begin. If someone is in a hurry, or can't keep up, or is limited in speed by equipment, law, or regulation, traffic begins. If any traffic begins to take effect, it rapidly compounds into a slower mesh in the best case, and a traffic jam in more realistic situations.

In all situations, the frequency of exits is inversely correlated to the efficiency of transit.

*: Whether the right lane is entitled to change lanes left, or must wait for an oncoming faster car to go by, varies. In the US, if the car can get in the next lane safely, they're legal. In Germany, if they cause a car to have to slow down for them, they're illegal. I favor the German system, as it forces awareness and has less reactivity, which can be hazardous. My personal rule is to never merge, turn, or change lanes if someone else will have to react to me in any way. It is infuriating when someone turns from a secondary road with barely enough time to get their car into the lane before I would have hit them if I hadn't braked.

TL;DR your anticipation of the proposed policy being derided was correct, and such derision is merited both from a safety and an efficiency standpoint. When machines are handling transit, it may become a more feasible solution, but that time is not now.