Yes.. I had a 1986 BMW that had central locking, electric windows, radio, power steering, cruise control and a thermostat (which, as OP said, mechanical anyway).

No microcontroller on that car[1]; it was a very reliable car too (bought it with 50000km, sold it with 270000km and only ever did services. Nothing broke in that time).

Bosch k-jetronic fuel injection, no microcontroller needed.

> mechanical door lock

Push button, engage solenoid, who needs a microcontroller?

> manual windows

Push button, turn on motor, limit switch to turn off the motor when you get to the end. Microcontrollers make pinch detection and calibration nicer though.

> no car stereo

Tons of examples here, a stereo built today would most likely have electronics and/or a microcontroller because it's cheaper than an analog FM radio, but an old one will still work fine.

> no power steering

On my 1978 vehicle. I believe this is hydraulic with a belt powered pump to reduce the user torque on the steering wheel. No electronics, certainly not a microcontroller.

> no cruise control

On my 1978 vehicle. No microcontroller there, just some vacuum linkages. Maybe a bit of electronics to turn things on and off, the switch certainly felt like an electric switch.

None of these things require a microcontroller. Because it's cheaper, almost all of them use a microcontroller on modern cars; thermostats on lower models would probably be the most likely to be a simple system without a microcontroller.

You can save a lot of cabling when you have central message bus shared by different components where a microcontroller decides whether a particular message is meant for this solenoid or that motor.

you also have a single point of failure, which is a double-edged sword.