Another way of putting what dlang is saying: newer is not necessarily better. The whole process of software development is an ever-broadening series of abstractions, and you need to choose good ones. Working with the abstractions you know can often be better than learning a new set that are incompletely thought out. The more advanced a toolkit is, the more likely you are to run into weird problems with it, either outright bugs or "leaks" in its abstractions.
There's lots of 'tools du jour' in the computer world, fads that come and go. Identifying the ones with lasting value is not an easy thing, and if you choose poorly, it can cost your company a very great deal of time and money.
If you try to jam prospective hires into a bad framework, you'll lose most of their value. By asking them something like "How much effort are you willing to put into Ruby on Rails?", you're short-circuiting a great deal of their experience. Ask them questions like, "We're doing X. How would you go about architecting that?" You may just find that their napkin solution is better than what you already have.