To provide a better experience for both package authors and users, as well as reducing the maintenance burden, the community has developed and migrated to a unified system called BinaryBuilder (https://binarybuilder.org) over the past 2-3 years. BinaryBuilder allows targeting all supported platforms with a single build script and also "audits" build products for common compatibility and linkage snafus (similar to some of the conda-build tooling and auditwheel). One downside of "cross-compilation everywhere" is that it's not always well-supported by upstream libraries, so the initial effort to build a library may be higher if patches need to be developed, but that effort is arguably higher-leverage than a per-distro packaging approach (eg https://twitter.com/Blosc2/status/1395425736597585920).
All that to say: "make binaries a distro packager's problem" sounds like a simplifying step, but there are some big caveats. It has been tried before, both in other languages and in Python: the fact that conda and manylinux don't use system packages was not borne out of inexperience. One additional issue is that distro packages are only available with sysadmin consent in shared unix-like environments, which can be very limiting for end-users.