https://www.youtube.com/watch?v=nQlFIl18x9g
Obviously I don't expect you to watch all of this but to have the lights working you need to program a computer to do so. This guy had problems just sourcing the right "module", then it has to be programmed. The car is basically an ornament until they fix it. This vehicle is about 20 years old and seems to be in reasonable condition for its age and would otherwise be perfectly fine to drive on the road. Now he is lucky to be friends with a guy that has access to the BMW software and has decent knowledge of how the software works.
Contrast that to my 1994 Land Rover Defender. There isn't a computer in it at all. The most complicated electronics is probably the wiper circuit and (which is partly mechanical). To fix electrical issues you use a multi-meter and adding/removing fuses. My toolbox is spanners, screwdrivers, socket set and a multi-meter. I managed to fix my vehicle in a car park at 11pm, with no prior experience of repairing this vehicle.
If you want things to be able to be repaired by normal people they have to be simpler and typically that means everything has to be modular with a well define spec or easily reproducible for a person in his shed with easily available tools. The trade off is that it won't be refined.