A removable insert can make a familiar pair of shoes feel less harsh without requiring you to replace it.
The improvement depends on more than softness, though.
The insert must fit the shoe’s interior, leave enough room for the toes, and suit the way your foot moves.
Memory foam can cushion contact under the heel and forefoot, but it may not provide the structure needed for every type of discomfort.
Before buying, identify whether you need a full insole with a heel cup and arch shape or a thin comfort pad that simply adds a softer layer.