Not for long. You can still do this with older cars, but newer ones really restrict you. I just bought a new car and am not even allowed to jump start someone else's battery without risk of voiding my warranty.

I don't know what car you've got but I have a brand new Mercedes-AMG and I can do a surprising number of things with it without voiding the warranty. It's certainly as easy to work on it as on older cars, I don't need to go to the dealership to replace the brakes, the battery, the bulbs, filters, engine oil, transmission and diff oil. Manual explains how to jump start the car but certainly doesn't prohibit it. I've heard some horror stories with newer cars (especially French and American) but it's not like all new cars are horrible to work on.

In large part thanks to the CAN bus and how jump starting is likely to cause enough spiking to fry the boards.

Was trying to help a relative with some issue with their car the other day, and the wiring diagram for the part and related controls almost seemed to run in reverse depending on how the switch was set.

doing work on your car always voided your warranty, with good reason. That's not a realistic thing to ask. It's realistic to ask for the UI and apps to be open-source (say, something like android), but even that would be an incredibly open thing for a non-software company to do. I still think it's very unfair to call them extremely closed.

However, I really do wish they'd adopt a more android-like ecosystem.