Never found a good application for any of these immutable js data libraries. Maybe it could be helpful to prevent bugs in middleware chains of expresslike backends but for ui libraries it always felt like the libraries basically recreate mutable data structures with virtual proxy objects but at that point what does immutable even mean? you have completely virtual objects and can do whatever you want to make the rendering performant and reliable, at that point it would look probably more like a data binding layer with virtual objects to something like tanstack query
Immer was made for React, so it's mainly just used to satisfy React's purity requirements (i.e. not mutating state values) with mutable-looking code, not necessarily for any other benefits you'd expect from immutability.