I worked on a product about a decade ago which had an unnecessarily complicated custom layout system written in javascript. CSS was missing a lot of features at the time, so we figured we'd roll our own. It was crazy complicated - and it had all these weird easy to reproduce bugs.
For fun, some pesky kid on twitter took our insanely layout system and reimplemented 95% of it in a couple hundred lines of (almost) pure CSS. At a glance, it looked identical to our product - but the code was small, clean and fast. The link got passed around the office. It was amazing how many reasons people had to dismiss it. "Ah, see - it doesn't even do this weird custom behaviour we have!" or "Well and good in chrome - but it doesn't work properly on IE8!" and so on. I've never seen a better example of motivated reasoning, before or since.
What we should have done is reach out and offer that kid a job.
The smartest programmer on your team isn't as smart as the smartest programmer on the internet.