Many third party companies have made accessories to read information or control devices using it. Cars also have a standard diagnostic port called the OBD2 which you can purchase $10 readers that use bluetooth with your phone.
Cars may have much more electronics but with all the sensors it's very easy to know what part of the system is broken. For example on my mom's 2011 Honda Civic (about 100k miles) her check engine light came on. I read the codes and it was the transmission pressure switch. I purchased one for about $30, replaced it, and everything is running fine.
As to all these new electronic systems and their value:
A 1964 Pontiac Tempest GTI has a 6.4 liter v8 engine that makes 348hp[1]. It goes from 0 to 60 in 4.6 seconds and does the 1/4 mile in 13.1 seconds. It gets 11mpg~
A 2022 Volkswagen Golf R has a 2.0 liter i4 engine that makes 315hp. It goes from 0 to 60 in 3.9 seconds and does the 1/4 mile in 12.5 seconds. It gets 23mpg[2] (26city 30hwy). It also has all modern emissions requirements.
[1]HP numbers were overrated pre 1990s because manufactures would remove accessories during testing.
[2]They changed how cars were rated in the 2000s so the 23mpg would be higher if rated back in 1964
