Can't say I've ever really thought of YAML as complex. Especially when the Ansible modules are translating things so you can just define the action you want to take, and each module is very well documented.
Embedding python in yaml has a ton of gotchas for cases where string processing doesn't quite line up with the way yaml wants things. Variable interpolation is also a real mess.
Typically the recommendation is to write your own python plugin/filter/test if you find yourself writing a lot of python in yaml, that way the yaml stays sane and readable, and just has some light Jinja.