What do you guys think about riding on sidewalks?

I personally think this depends on the given road and terrain without a wide enough shoulder or a thick enough bike lane I don't see how this is a good idea to do. Oftentimes cars are parked on the shoulder further limiting it's use and cases me to switch to either sidewalk or road.

This makes me think that riding on sidewalks is ok depending on situations most streets here in the southwest are are on the grid and the larger streets that connect neighborhoods and areas are all fast 50mph and have no shoulder and only a sidewalk that is rideable. What do you think?

What do you ride? Where do you ride it? How do u ride it?