the more I see a city designed around the car
Edinburgh's problem is not that it was designed around the car; it wasn't, there's precious little of the city centre layout that is any newer than early Victorian, and then there's a good ring around that that is all pre-20th century. The problem is that we've tried to shoehorn the 20th/21st century motor traffic into the medieval-Georgo-Victorian layout that was never meant to accommodate anything other than horse-drawn traffic.
The Georgians didn't build wide streets for any other reason than they liked wide streets and grandiose design gestures. Edinburgh's planners look upon this aesthetic gift our predecessors left us and go "ooh, goodie, median and road-edge parking AND 2 lanes of motor traffic each way". They also had no concept of managing traffic flow, so these wide streets only connect to narrower, less-grand streets at each end.
With all these cars being encouraged into and through the city centre, the only way it's even remotely possible is to hugely downgrade the time and priority given to people on foot with infrequent and inconvenient crossings of the main roads.
Someone from MCC observed that Roseburn Terrace was 100 years old, which is true for the majority of the tenements, but the road width and layout is quite a bit older than this, the "new" bridge was built in 1841 when the road was straightened away from the alignment to the old bridge, the road to Corstorphine and beyond along this route goes back further. It's the route Davy Balfour takes back into town in Kidnapped and even before the oldest maps and the lochs and marshes were fully drained this was the main route to the west - there used to be a series of beacons along the route to guide travellers along the safe passage at night (I believe Corstorphine Kirk still has a bracket for one of these). So really we're using a medieval route into town.