Cars don't suffer feature creep. We've optimised them - removed the horse, switched to steel construction, added electrical subsystem - but really there's been no major functional change in cars, ever.
...added electrical subsystem, replaced combustion engine with batteries and electric motors, we're adding various degree of autonomy.
In parallel, we've replaced sane controls with frustrating and dangerous touchscreens, we've added countless types of comfort features, we've improved security, we've computerized engine controls, we've DRMed the car - ostensibly to prevent theft, but actually to route more money from aftermarket towards the manufacturers. Etc.
Cars do suffer feature creep, and not all of the features are beneficial to their owners. Just like with the web.
Our expectations about cars have definitely changed over time. I don't think it's even legal to sell new cars without seatbelts, something that did not exist when cars started. Even low end cars in the US have added features compared to low end cars of the past, such as power windows, power steering, power mirrors, and so on.
It's true that adding features is slower in cars, but that is because cars are partially hardware. It takes much longer to add features to hardware, because making copies is not free. But that does not mean they are unchanged.
Nope. Cars have advanced, but if they were webtech, we'd be wondering why they've not implemented OrbitalMechanics support yet. OceanMechanics would be old hat.
"When will car technology be complete?"
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The answer is they wont be in short term, and they will be made obsolete in the long term.