No, I think your conclusion is reasonable. Although I think modern electronics are very reliable, I also think that they are effectively irreparable when they do fail. In terms of sustainability, the carburettor is surely the way to go.
Now, about electronic ignition. Are you certain that you can find a system that's as reliable, or more so, than the original ECU? If reliability and repairability are of primary concern, you should probably revert to points-based ignition.
Realistically that wouldn't be practical, so you will need to carry a spare pickup and ignition module with you if you want the ability to repair by the roadside. Are you willing to do that?
I don't see why carrying a spare ignition module would be objectionable. It's small and inexpensive. I'm not sure this is the correct one, but I would probably purchase a spare, right up front if I was making the conversion.
https://www.ebay.com/itm/195799258167The pickup coil seems like there is little to go wrong, and might even be repairable with a bit of patience. But again, small and cheap, so why not keep a spare?:
https://www.ebay.com/itm/295139818166But, I don't think it would be necessary to carry. It seems to me that an ignitor that would work adequately, although it might not be identical and would require hacking the wiring, could be pretty easily found in any number of motos from the 70s onward. And there are all sorts of options on Amazon, just a day or two away. Perhaps this one, from a Suzuki single, would be quite adequate to make sparks:
https://www.amazon.com/Amhousejoy-Motorcycle-Ignitor-Digital-Ignition/dp/B08B4S913J/ref=sr_1_2 And my thought for self support while on tour, was not that I would carry everything I might possibly need, but rather that I would HAVE everything that MIGHT be needed, nicely organized, and if I ran into trouble, I'd call my friend back in Chicago, and have them overnight express me "box C-12", which I knew contained the part I had forseen might fail. This same technique could certainly be applied to the original EFI system, but the cost of this advance planning becomes quite a bit higher, due to the longer list of more expensive components.
Sallying forth, without all this planning and relying on the basic reliability of the parts is probably fine. Certainly people do it. To Steve's point, these electronic components are very reliable. On an HD, a Honda or a Yamaha cruiser, that sold well in this country, I wouldn't think twice about taking my chances, relying on the fact that spare parts were probably not going to be hard to find, if I had the very bad luck to experience a failure. But, with the RE single, relatively rare in the USA, I would be surprised if a replacement for certain parts was NOT an issue. I suspect that this isn't the case at all for the 650 twins, the 350s, and the Himalayans, but these are all in current production and mainstream distribution.
What we do, when we change from EFI to carburetor, the hard way, is to go from an electrical system that has 8 or 9 points of potential failure, (and substantially more if we count the wiring and connectors)
ECU
Fuel Pump
TPS
Pickup coil
MAPS (if equipped)
Temperature sensor
Lambda (02) sensor
Injector
Ignition Coil
To a system that has three. This seems inherently more reliable. I wouldn't be surprised if the most failure prone element of the electrical systems, are the connectors. Less is better.
TCI
Pickup coil
Ignition Coil
I think it's valid to say that we will have given up some potential electrical failures for more potential mechanical failures in the carburetor, but the high pressure fuel system and its required regulator are unique to the EFI system. In my opinion, mechanical failures are much more common than electronic, but are easier to fix.
Declaring either as "more reliable" overall would be a complicated analysis. I'd be going more for "more REPAIRABLE, with only parts from Walmart and working under a tree on a piece of cardboard", which is what I believe the mostly Indian proponents of "never EFI!" were also going for. It took over a decade, and several emissions regulations updates, but that argument seems to have subsided.
Still, it does seem a little odd that carburetors on motorcycles may have survived longer in the new world, than in the old.
https://yamahamotorsports.com/models.php?product=259&action=features