So the target user of new bike infrastructure here is not so much the strong confident riders, but the beginning, slower, inexperienced rider. Basically, imagine granny who rides 10 mph on the bike path, or little Jimmy who just turned 9.
I think that for granny or Jimmy, a good bike lane is a lot better than dodging cars in the traffic lane; a marginal bike lane is still better than dodge-car; a physically separated bike path is great. Frankly, if you tell them "bike infrastructure is dangerous, ride in the traffic" they just won't ride.
And yet, the only place I've really seen much of Jimmy and his grandma over the last several decades is on totally segregated bike paths and a bit on very quiet residential streets. They don't seem to venture out on the sidepaths (grade separated bike paths on multi-lane streets; often kind of a sidewalk) or cycletracks. It could be the lack of complete connections that is holding them back, or it could be that these implementations aren't as attractive to them as their proponents claim, or something else or both.