YAML isn't a programming language. The fact that it's often abused to be one is not the fault of the syntax.
The problem is when you use YAML (or an ad hoc interpreter embedded in YAML, or a templating system built on top of YAML) for things that should really be a programming language. Things like imports and functions and composition are useful. Templating is a more ergonomic form of string concatenation.
However, if the config is a travisCI YAML file that is really just a glorified list of commands I don't think bash or a makefile is a bad solution. Take as much as possible out of the CI config and use a neutral standard format like a makefile to encapsulate much of your logic.
Then when TravisCI stops offering free usage for open source, its easy to move, because your format isn't specific to a vendor.
The visionary executive team at a certain company I worked at felt otherwise and poured millions and thousands of eng hours into recreating HTML/JavaScript MVC components, but with YAML