Going back to carburetors, vacuum lines, and choke valves? I can't even imagine what that would do to air quality around us. If you remember cars in the 1970s, it was awful.
I've never seen an ECU you couldn't tune with a laptop. It's a hell of a lot easier to dial in a modern engine than it was when you had to try to find the best combination of jets, needles, and springs.
You usually need more than the electronic equivalent of a screwdriver though, right? Maybe I'm mistaken. I was under the impression you would typically need something like a Cobb port.
If you can access them, I certainly imagine the efi profiles are much more tuneable.
Yes, it's usually a fair amount of work, on most modern ECUs there is some form of signature based protection which will require an exploit chain to bypass, and then the need to write either software patches to enable introspection into the parameters necessary to tune, or to reverse engineer the protections on the factory calibration protocols if they were left in production builds. This is all possible with the electronic equivalent of a screwdriver, a Raspberry Pi, but requires a lot of reverse-engineering effort and understanding.
Modern engines heavily utilize chips. Solenoid valves everywhere. Also your steering, brakes would need some sort of chip.