Being one that gets a mail for every comment/issue/PR/etc in the restic repository I can tell you that there’s a lot of work, not to mention thought, going on even if it may not seem so (including for the prune command). I personally think the next restic release will be quite an improvement 
The fact that there’s some years-old issues and PRs is mostly due to us not wanting to straight off close the ones we don’t envision merging soon (we’d rather keep them around for various reasons) as well as there being a lot more work to dealing with even seemingly simple ones than most people probably imagine. Writing code is easy, reviewing and making sure code won’t break things is hard and takes a lot of time, even for seemingly simple things. Not meant as an excuse or anything, just saying there’s more to it than one might think.
I have your VSS thing (assuming yours is the one I’m thinking of) on the radar, it’s one of those I’d like to get merged sometime soon. But there’s still not a lot of testing having been done on it, and if I’m not mistaken someone reported a 32-bit problem with it just the other day, so it’s not entirely straight-forward.