there's quite a bit loaded in your term of "computer" that doesn't really work. if a watch or headphones can eventually be called a computer, then a software-based car running on a battery can certainly fit under that definition.
If self-driving had worked, and a fully vertically integrated tech stack could have controlled your “mobile experience” end-to-end, maybe a different story.
“Siri, take me to pick up Grandma from her flight. Let me know when she lands and send her an iMessage when we’re five minutes away.”
Outside of the premium brand/build quality, I think Tesla was actually a successful proof of concept of what they could have done or could do. Computer/software-powered, battery-charged, integrated hardware/software, principled product tradeoffs, new retail model, advances in charging technology. Big parallels to the first iPhone. You even heard the same complaints from consumers when the first iphone came out ("I want my buttons/physical controls back", "The battery/range dies too quickly"). Apple may not want to be in the car business, but I think Tesla showed that cars could just be computers now
But I think Tesla shows the limits of Apple’s approach in the car market: Imagine a Model S that is maybe 50% better across design, materials, features, UX. That’s still not a “leapfrog” product the way the iPhone was years ahead of the smartphone competition when it was launched. It couldn’t justify also being 50% more expensive.