Well my pet hate is that I write a lot of YAML. It's poorly structured, unreliable, nuanced, schemaless and difficult to edit reliably. I prefer XML and XSLT to this shit show. Oh and unnecessarily distributed things.
In summary, apparent simplicity that causes actual complexity is a big problem now.
I'm still surprised at the apparently unanimous disinterest in a tabular format for data serialization languages. XiMpLe took me way too long to find. I can't recall if it works on YAML, though. But it removes a lot of the headaches for me.
In summary, apparent simplicity that causes actual complexity is a big problem now.