The Original Poster (OP) actually inadvertently answered their own question and made the point for the opposition. Some countries do issue an automatic-transmission-only license because it is SLIGHTLY easier to drive automatic than manual transmission. No country issues licenses to drive while blindfolded.
The OP made the assumption that modern avionics make it easier to fly Instrument Flight Rules (IFR) than Visual Flight Rules (VFR). Which is true as long as you are flying in Visual Meteorological Conditions (VMC).
The hard part about IFR is the increased workload involved in adhering to IFR procedures. Modern avionics alleviates some of that, but not all. The parts of flying that flying IFR makes easier, it makes slightly easier. Just like an automatic transmission. The parts of flying that flying IFR makes harder, it make many times more hard. It becomes infinitely harder when flying in IMC. And, when (not if) your avionics malfunction, it infinitely compounds/multiplies the difficulty even more.
To fly an aircraft you have to Aviate, Navigate, and Communicate in that order, while you constantly mitigate danger and risk at all times. Flying IFR with modern avionics helps you Navigate. Following explicitly a cleared IFR plan, IFR charts, and IFR procedures will mitigate risk of terrain and obstacle avoidance. Once you file and receive clearance on an IFR plan, being “in the IFR system” helps you Communicate because it keeps you in communication with Air Traffic Control (ATC). ATC will help you mitigate the risk of traffic avoidance and separation. That leaves the most important part, and number one priority of flying, Aviate.
To Aviate is to FLY the plane. Aviating is to manipulate the controls in a proper, effective and safe manner. It is to have positive control of the plane’s performance and flight path/direction at all times. You mitigate while Aviating by checking, cross-checking, and double-checking every part of your flight and flying, redundantly. That includes: you and your actions; the aircraft and it’s reactions; the performance of all systems and components; and the list goes on. As a pilot, you then have to interpret the meaning of the information you receive and adjust accordingly. You do this whether it is you, your copilot, or the autopilot (George) actually flying the airplane.
In VMC, you Aviate the same on IFR as you do on VFR. You utilize the two most important instruments at your disposal, your eyes and the windscreen. You look outside 75 to 90% of the time because that is where the majority of your pertinent information is and your concentration should be.
In IMC, you lose that 75 to 90% of information that you need to fly. But, you still have to Aviate. You have to rely on and trust in ONLY the instruments of modern avionics. You have to continue to mitigate, cross-check, interpret, adjust, all the tasks of Aviating with the majority of your information gone. You also have to recognize when your modern avionics (which are made by fallible man and prone to wear) are not giving you the correct information and adjust your actions accordingly. In case your modern avionics become inoperable, you have to piece together what information you have to keep Aviating. This is especially true when you are on autopilot. Even when you are not flying the plane yourself you have to monitor everything. George is not perfect.
All of this takes more equipment (avionics) in IFR than it does in VFR. More importantly, it takes special, intense, and ongoing training for the pilot. To ensure this happens, you have to put it in a legal and enforceable framework. You require the rating and it’s recurrency stipulations.
Think of it like golf, darts, archery, whatever you are in to. In order to get good at it, you have to get the proper instruction and coaching. Then, you have to get the proper practice. Except in aviation, you have to get a hole in one or bullseye every time. And, your life and the lives of others depend on it.