I understand the sentiment, and truly I can see both sides of this. But here's where I'm coming from:
Washington Street is a street. Not a charming little alley with restaurants and shops like you'd find in Rome or - try this link -
Seville. Notice how the scale here creates a vibrancy that even a few people can successfully activate. Pedestrian zones NEED to be pedestrian scaled (and the exceptions to this rule, like
Plaza Mayor in Madrid, are in my mind exceptions that prove the rule: they're explicitly built with the idea of overwhelming and overawing the pedestrian with the vast open space WHILE still managing to somehow feel cozy). Now, check out this
main drag in Oxford, UK - this is pretty much Washington Street. It's the lousiest, trashiest, most de-energizing spot in town, despite being smack dab in the middle. Streets are built and scaled to be complete. A street without traffic feels desolate, detached from the city. Now of course I'm not advocating to make Washington Street into a highway. But to allow cars down it, perhaps in a woonerf format, would be the right move to get things moving in the right direction.