Except that here in the Netherlands sidewalks are both legally and by design something that is used alongside cycleways too. Sidewalks often continue from running beside a road to running beside a cycleway. Mateusz is used to combined foot- and cycleways, which we don’t really have, but are common in countries that do not yes have as progressive a policy for road layout favouring cyclists as we do.
We have, ignoring rare exceptions, cycleways that either explicitly allow pedestrians because there is no sidewalk, or which do have a sidewalk which is then mandatory for pedestrians.
Of course we do use segregated=no, because it was pushed by validators, and because all of our G11, G12a, and G13 cycleways without a sidewalk are foot=yes and segregated=no by definition. Excepting rare cases, we shouldn’t need segregated=yes because sidewalk=left/right/both already implies that.
A big drawback for the Netherlands is that a combined foot- and cycleway is aligned in the middle of both ‘lanes’, whereas streets and cycleways with sidewalks are aligned in the middle of the carriageway (i.e., the middle of the cycleway for cycleways).
So with sidewalk=* tags you would align the cycleway like this:
Without sidewalk=* but with segregated=yes you are declaring it a combined foot- and cycleway, and would have to align it in the middle of both. This goes against current mapping practices, and leads to weird jarring transitions where sidewalks stop or branch of (as is the case here).
For the Netherlands, sure. But I would caution against adding sidewalk=no everywhere, because a large portion of our cycleways lie outside of build up areas and tend to have no sidewalk. Similar to general roads, many mappers dislike adding sidewalk=no to each and every road. In those cases segregated=no seems more useful because it is already part of presets and validators. When there is a sidewalk, sidewalk=left/right/both is good and segregated=yes is then implied.
I would also ignore all cycleways with segregated=no. Those imply the absence of a sidewalk already.
Don’t forget to consider sidewalk:left and sidewalk:right too, so StreetComplete shouldn’t ask for cycleways that have those tagged with suitable values already.