> it won't include the cruft that we now know was bad cruft.
There's no such thing as "bad cruft" - all cruft is are features you don't use but are (or were) in all likelihood critical to someone else's workflow. Projects transform from minimal and lightning fast, to bloated, one well-reasoned-PR at a time; someone will try to use a popular project and figure "this would be perfect, if only it had feature X or supported scenario Y", multiplied by a few thousand PRs.
There's no such thing as "bad cruft" - all cruft is are features you don't use but are (or were) in all likelihood critical to someone else's workflow. Projects transform from minimal and lightning fast, to bloated, one well-reasoned-PR at a time; someone will try to use a popular project and figure "this would be perfect, if only it had feature X or supported scenario Y", multiplied by a few thousand PRs.