We look at engineer hiring to determine what's valuable, and what's teachable. Do we want our engineers to be current? Yes, but only reasonably so. Anyone who has been around long enough will recognize that most currently popular technologies in use as tools of the trade are simply iterations on ideas that have existed for a long time. Any individual who thinks we're in the dawn of some amazing age where the tools are only understood by a certain generation is, for lack of a better word, foolish.
So, for us being current is really just status at a point-in-time. It's entirely teachable (or better yet, learnable.) But what's valuable? Understanding your trade is important to us, but having real experiences under your belt is super-critical.
Have you ever run a large-scale operation where your code was mission-critical? That's important to us. Ever been responsible for deployment that required zero downtime? That's important. Ever had to ship code and the difference between success and failure meant revenue and jobs? That's important. Ever actually done more than one thing besides {web/mobile/admin/etc.}? That's important.
So, we try to combat ageism by ensuring we give young folks a chance. Not everyone gets that opportunity, but we do so sparingly when we feel such an investment is worth our time, money and effort.