Crank Sensor

A mechanical distributor is two independent 2D curves. A 3D timing table is much better. There are many desired tuning capabilities, not possible with mechanical distributors.

A 3D table lets you control vacuum advance at throttle release at high RPM, or coast down light throttle conditions. The ported throttle vacuum source is a poor control. There are many more improvements, related to starting, temperature controls, mixture interactions, knock controls ...

There are likely ways to tune the OEM PCM by reflashing or other means. I developed my own ECU, so never tried.

I have never failed an ECU in over a decade of working with them. Things like TPS or other sensors likely go first, based on my experience of repairs on OEM systems.