What should restic do differently? Which functionality do you think we should add?

restic prune currently does both pack deletions and rewrites. Pack deletions are fast but rewriting is slow, and requires fetching data from the backend (#2162). This fetching is very expensive for some cloud storage options (B2, Glacier, etc).

A new prune option to skip the repacking step and only delete entirely unneeded packs would allow faster incremental pruning operations.

What are you trying to do?

restic prune against b2