I write Python for years (including messing code) and never feel the pain I found when I edit an even a slightly complicated YAML file.

The issue is not really the significant indentation of YAML, it is more of the ambiguity of the syntax plus the fact that YAML is a serialization format so it doesn't have many ways to reduce repetition. Now those issues coupled with the significant indentation makes YAML a mess, but those issues doesn't exist in Python.