I'm not so convinced that YAGNI generally leads so directly to "elegant, short, and easy to maintain code" as you say. Certainly, with a very keen sense of when to make the transition from Ain't to Are, it can lead to time-savings and simpler and more focused code, but with less discipline or tight deadlines or (typically) both, it can also lead to repetition and the complexity of maintaining many one-off features, even if each is relatively simple in itself. Something very similar can be said for a more architectural philosophy - with a very keen sense of when a design is liberating and when it is burdensome, it can lead to less repetition and targeted maintenance, but with less discipline it can lead to analysis-paralysis and over-engineering. Like most things, the best answer is somewhere in the middle.

My preference is YAGNI while keeping a sharp eye on things that are relatively hard to make extensible later and relatively easy to make extensible now. To tack on another not-great example to the not-great Dog example - if I find myself writing 'dog' a bunch of times in a bunch of ways, I may well pull that out into some sort of `type` variable even if I-ain't-gonna-need-it.