I was thinking more along the lines of every second street in one direction having a separated bike lane with full right of way at conflict points and infrastru

I was thinking more along the lines of every second street in one direction having a separated bike lane with full right of way at conflict points and infrastructure to manage the cars (like raised crossings and/or lights) so noone would have to cross a road at an undesignated spot more than once to get to it. You can even arrange it such that there is no through traffic on some cross roads (bike lane in the middle and all entering cars must turn right in RHD countries) to reduce the number of conflict points (with cars only crossing the bike lane every km or 2). But the alley way type arrangement you're thinking of has existed in the past as well (and probably still exists in some places) with a narrow alley enterable through the back yard that cars only enter if they live on that block. Additionally it's not really a burden for the cyclist to walk for the first/last km or use the sidewalk at jogging pace where that is legal (so long as the sidewalk road crossings are built with similar levels of safety and pedestrian priority).