> How is gold plating the same as YAGNI? They're opposites, no?

No, gold plating and YAGNI are two faces of the same abstraction coin.

Under-engineering is not the same thing as YAGNI.

I worked at a place where the former employee had engineered his whole S3 to files synchroniztion layer. We never needed that. That's YAGNI. (And if we did, the library already has it!)

Choosing crappy overly-simple ideas for abstraction is not what YAGNI is all about. It's about pulling in overhead+complexity when it's justified, and only then.