Stuff that gets too complex you can pretty easily abstract into a role and jump into Python.
https://opendev.org/zuul/zuul-jobs/src/branch/master/roles/t... is a nice example of some pretty complex co-install of libraries for testing under tox (and you can unit test bits of it too...).
https://zuul-ci.org/docs/zuul-jobs/ is a collection of roles and playbooks that do a lot of complicated things with nice abstractions such as this. Although they're designed to be called from the Zuul CI system, there's many good examples for anyone wanting to build out their Ansible in a scalable and maintainable way.
I'd like some kind of 'sensible', backwards compatible layer in Ansible that would allow me to rewrite stuff in raw Python, with 'normal' code, where it makes sense, but keep YAML for constructs that do actually look and work like lists of basic tasks.