So what manufacturers do seem to care about security? If I wanted to buy a car made in the last few years, who is least likely to be cracked?
If you're worried about safety, buy a car with a good crash safety rating. You're far more likely to get into a normal crash due to bad human drivers or mechanical failures than you are to be hacked.
If you're worried about the financial loss from a crash or theft, your best protection is good insurance.
Not for long.
But I really doubt that all the thieves out there will learn fancy technology so they can steal newer cars. A few will, but most will find other things to steal.
Right now, popular new cars are stolen in amounts of hundreds per year in the US. Older cars (like the Honda Accord) are stolen by the tens of thousands. That's not because older cars are more valuable, it's just because it's a lot easier.
By saying a thief would have to understand how a computer exploit works, it's saying a thief needed the equivalence of an engineering degree to drive away with a car before computers entered the equation. Exploit discovery, maybe, but it doesn't take much to execute packaged tools you bought on the blackmarket.
Whatever the reason, stealing newer cars is harder. That increased difficulty translates into decreased theft rates.
For now. Once they get out of circulation only newer cars will be left and at that time it might be that thieves could buy devices to hack into these cars just as you can rent botnets today.
No one is going to crack that but a guy with the right piece of plastic can still take down a window, get in, and steal the car. If someone wanted to murder me, they'd need physical access to the car to mess with it.
So...yeah. No situation is 100% safe or secure. However, pretty much anything wireless pretty much guarantees any criminal can just make a kit to do X and sell it to actual car thieves claiming he thought they were [legal profession like car repo].
Sort of like how people sell malware/"security tools" now. "Oh, I sold it to a criminal. HOW COULD I HAVE KNOWN?" :p
For affordable options, I have no idea.
Until then, buy a Lada Niva. No one will want to steal it and it doesn't have anything complicated in it that can be hacked.
Get an old American junker.
There are very high-end car thieves who want flashy cars, but the vast majority of car theft is about 1) ease and 2) what the parts are worth.
Radio keys should be OK although they have their own security risk.
Pro-Tip: If you're chaining your bike up, make sure the chain can't touch the floor.
It has been this way for about two decades. It is much easier for thieves to slice-and-dice a common vehicle into hard-to-trace parts, since the hot parts will disappear into a sea of legitimate used and reconditioned parts. High-end cars are comparatively rare, and thus harder to dispose of discreetly.