It would be interesting to see what the most common compile feature checks are for, and see what alternative ways could be used to make the same information available to a build system — it seems like any solution that requires libraries being updated to “export” information on the features they provide would have difficulties getting adoption (and not be backwards compatible with older versions of desired dependencies).

From my experience looking at rust builds, Pareto applies here: most checks are trivial and used by a lot, and a handful are super complex and niche.