Packaging Python apps really really sucks - at least for Debian there's stdeb - https://pypi.python.org/pypi/stdeb/0.8.5. No idea if it's lintian-clean though.
Https://github.com/alanfranz/fpm-within-docker for native packages.
All that while writing RPM specs and proper(ish) debianization are quite easy.
Systemd is far from everywhere. Ubuntu 14.04 doesn't use it and is supported until 2019. Debian Wheezy is supported until 2018. RHEL 6 has support through to 2021.
Overall this means it'll start to be reasonable to presume systemd sometime around 2020, and be realistically almost everywhere from say 2025.
Software changes take 5-10 years to roll out everywhere. This is such a core change that it'll be on the longer side.
And that still doesn't change the fact that most programmers produce shitty packages, if any, so every time I use somebody's software I need to package it myself to have it properly built.