A fusible link is more like a fail safe, it won't react as fast as a fuse, can handle more loading, but it will break before the wire it's attached to.

A 20 amp fuse will open right at 20 amps on average, sometimes 18 or 19 too. The fusible link will error on the other side and for a longer time. But it will open before the wire it is attached to. And they were usually installed as part of the feed to the power supply. I've seen them used to protect fuse panels too.

Like many things, they have a place to be used and a place they shouldn't.