There are ways to do residual current detection that don't involve microelectronics. Not as sensitive as a GFCI, but I am sure you could make a device that detected 10A ground faults that was as reliable as a thermo-magnetic breaker.
Rather than solidly grounded systems, you could have resistance grounded systems where fault current was limited to say 10A or 50A or some easily detectable but still relatively low value.
Or today I think it would be entirely plausible to have 'GFCI everything' and a resistance grounded system for normal residential use. I wouldn't mandate it, but would be delighted if it were an available/allowed option.
-Jon