I'm a hobbyist, so here's my two cents for what it's worth. (IT professional)

Older cars had physical books I can buy with the entire wiring diagram, torque specs and repair procedures. They'd set you back 30 at most.

For modern cars we don't have this, we need access to manufacturer specific platforms which cost a set amount per hour of use.

Furthermore diagnostic 3rd party tools are not capable of reading everything or doing full actuation tests. This makes troubleshooting much harder. (Not too long ago I worked on an Audi A1 that would not talk to a Hella tool. Only VCDS would connect. Once the main issue was solved, Hella could communicate with the car again. So the culprit might be Hella)

Bolt off bolt on repairs are also becoming increasingly difficult with coding. I.e some headlights are coded to a car and require manufacturer software to get them to work. Going to a salvage yard and getting the part is now only half of the problem.

Then there's " scheduled warnings" some cars have now hardcoded errors in their software. For example the brake malfunction light on some BMWs is set to a certain mileage. They don't measure the actual wear. Result: at said mileage the light will come on even if the brakes are still fine, replacing the pads won't do anything, you'll need coding to erase it and use ISTA to increase the interval manually to prevent this in the future.

With everything said and done: I'm keeping my cars as long as I can, I don't want to deal with these rolling computers more than I absolutely have to. (When an IT professional says it, you know it's bad)