I want to be clear, I'm talking about the city metro areas. Not commuting from suburbia. We should have fully separated bike paths for longer distance commute bike traffic, because mixed speed traffic with cars just doesn't work when cars are going faster, and unprotected bike lanes are just a bandaid solution to that problem.
But once you're in the metro area, everyone should slow right down. The dominant traffic in the city is foot traffic.
Cars go at 50km/h through my city, meaning they need to be separated really strictly. Slow them down to 20km/h with narrower roads, and you can reclaim the area for mixed pedestrian traffic, allowing more free movement for everyone in the city. Something as simple as crossing the road shouldn't take 10 minutes for 200 people just so five cars can cross the road.
With narrower streets and slower traffic, you can reasonably cross the road anywhere you want. That also allows bikes to move reasonably along the road but slowly on the footpaths, you open the whole area up for the people using the city.
It's all a balance, not everywhere in a city should be like that. I'm just advocating to move away from the heavy car-oriented lean many places currently have for their city centers.