you are correct. It can be very complicated. Yet people still think we can "pull a code" for free and wala, we know whats wrong with it. lol
What people need to understand is that pulling a code should NOT be free. The equipment to pull the codes was
not free so customers need to expect to pay for the equipment and diagnosis time. I have
VCDS for the family fleet and when a fellow dubber needs a scan, they know right off the bat I get $25 to give them their codes on a thumbdrive (text file or $30 with paper printout) and
additional fees to do other things like turn off DRLs or synch TBs. Auto'Reillys have kept the O2 sensor industry alive with their "free" scans...
The VCDS or other more complicated diagnostic scanners (Autel, OBD11, etc)
DO help with diagnosis in my opinion. You can get deeper into individual modules and sensors and the like with more conclusive results than a $20 generic code reader. But the customer MUST pay...
I typically tend to drive peoples cars harder than they ever will. Partially for reasons aforementioned, but mainly for fun.
Sometimes you MUST drive harder to achieve the correct diagnosis. And
if it breaks, the customer must realize the
value of the car being under the "care" of the tech when it happened.
My dot's BF works at a Hunday dealer. Roadtesting a 2024 sedan (whatever the model was) a couple weeks ago, he is in the left lane of two lanes doing about 40mph and someone pulls out from the right driveway and slams into his right side, flipping the car!

Car was totaled but the air bags My Pillowed his body and he walked away with only minor bruising from the seat belt.

At the hospital everything checked out fine (CTs, MRIs). Totally the other driver's fault which they admitted. I suppose the car owner will get an even NEWer car out of the deal...
A dc electric motor is a relatively simple device mechanically. The only parts that wear out are bearings.
But to CREATE a
durable electric motor (other than a simple science experiment) is a very complicated process and requires great precision. And just about impossible to repair "in the field" (ie: winding or pole issues). But with time and material, a machinist/welder/etc. can re-create a 100yo piston or casting for an ICE.
Your "magic fuel" comment got me thinking about this series called "
The Colony". A hokey and scripted
"reality" show, it was obviously piggy-backing off the popularity of The Walking Dead, sans zombies. But it was more likely a believable apocalyptic survival scenario than the zombie show although my scenario would involve (lots of) firearms.
In one episode, I recall them distilling alcohol out of pig guts or something. So a SIICE could conceivably run off that or a CIICE off of vegetable (or waste) oil in the apocalypse...
To us car guys, taking the real drivetrains out of cars is basically taking out the SOUL of what makes it a car.
The stuff nightmares are made of...
View: https://www.youtube.com/watch?v=cJHIIU_Vkl8&t=44s