(warning, beer-fueled rant to follow)
If that is a problem to you then you are doing it wrong. Let me explain by way of example.
Whether it's "easy" or "simple" or not shouldn't matter--
I shouldn't have to do it in the first place. None of the cars I have ever driven, not even the oldest ones that were about my age, have required me to pay any attention to fuel-air mixture or any other parameter unless something was wrong. I've driven cars over nearly as wide a range of altitudes as any airplane I've flown, with constantly varying throttle settings, and never once had to give the slightest thought to fuel-air ratio. And all of these are cars that, brand new, still cost less than just the engine that I'm putting in my airplane.
There's no reason an airplane engine should be any different--and in many airplanes, it isn't; turbines don't come with mixture knobs, even the ones with all-mechanical engine controls. I want to get in and
fly, not babysit an engine, and not play flight engineer. And since we don't have to worry about all the complicated emissions reduction stuff that cars and trucks do, it makes the control issue simpler. Simply program the controller to provide the lowest possible fuel burn for a given power setting while keeping temperatures within normal limits and not causing damage to the engine. As long as I'm not damaging the engine or causing a temperature issue, why would I ever want to burn more fuel? This is the kind of thing that automated controls are made for, and they do a lot better job of it than humans do once properly set up.
Besides, what advantage is gained from full-time manual mixture control? "Simplicity" is often claimed, but there's more than one way to look at simplicity--and operational simplicity, while sometimes ignored, counts just as much. What problem does it solve? What advantage does it gain me to be fiddling with something else in the cockpit right at the times when my workload is likely to be higher, like right after takeoff or in the pattern or in maneuvering flight with lots of power changes? To me, it seems like this level of manual control has a lot more potential for pilots to
introduce problems that otherwise wouldn't exist (how many engines are driven to early overhaul, or fail in flight, due to improper mixture management? How many thousands of gallons of fuel get burned needlessly because pilots don't want to, don't know how to, or for some reason can't run at an optimum LOP condition? and for that matter, how many airplanes get totaled every year due to carb ice, which could have been obviated by not having a carb in the first place?) than it does to save a pilot from something they otherwise wouldn't catch. Yes, there are failure modes that might require pilot intervention to save the engine, but for those instances an override can be provided, and requiring full-time manual mixture control under all other conditions isn't going to make that problem any less likely.
The mixture knob, like the vacuum gyro, looks like another one of those solutions that was developed a long time ago (100+ years, in this case) because there just wasn't any better way of doing it at the time, and there continued to be no better way of doing it (or at least, no affordable way of doing so) for a few decades, up to and past the "golden age" of the light airplane. It's become one of those things that we have just accepted as normal despite being incredibly anachronistic, just because 90% or so of the light airplane fleet was built before any other feasible means of doing it was available. That still doesn't make it the "best" way to do it.
We in the light GA segment like to gripe about being stuck flying behind 1930's technology in our engines--but then if anyone suggests actually
doing something about it, we gripe about
that. IMHO, after modern glass EFII-like systems
appear to represent the biggest bang-for-the-buck improvement in real-world operational efficiency and simplification that we're going to see for light airplanes, especially if we constrain it to things that can be relatively easily retrofitted to existing airframes.
I don't think it's too much to ask that my brand-new airplane be caught up technologically with 1980s automobiles, especially when you consider that the technology I'm going to be putting into the panel is quite recent, and has features that were bleeding edge, still-in-R&D level when I started my career testing integrated avionics packages for high-end jets.
Unfortunately over time pilots have been taught by instructors who knew no better, and just made simple things very complicated and scary for the pilot, because the instructors were scared themselves by old wives tales.
I wasn't taught to lean by my instructors, because in the tired old underpowered C150 I trained in, the throttle went to full rental power at takeoff and it didn't move again until you pulled the power on downwind, and the hourly charge was the same whether I leaned or not. The mixture knob was simply used to shut the engine off at the end of the flight.
That same old 150--the good one at the flight school, because it had a text-only GPS and was in marginally better shape than the other one--met its end between a pair of trees six weeks after I flew it for my checkride when that "simple" carburetor iced up and both the CFI and student forgot the carb heat. A perfectly good airplane ruined because of a simple oversight regarding a manual engine control.
