The best tuner capacitors are sealed and use a real vacuum. Those tuner caps in old radios *are* the cause for drifting. Ceramic capacitors weren't usually in them, mica was. Some old tubular ceramic capacitors were used, but they didn't drift like disc ceramics.

Better tuner caps use mica or poly film between plates. Better still to tune with a crystal or a digital synthesizer. Leave the tuner caps for use as long wire resonators aka antenna tuners.