The IRS will always accept a tax return, however, they won’t pay a refund if it is more than three years late. You also won’t be able to use TurboTax to file a 2014 return since that old version is no longer supported.
The reason you might want to file a 2014 return is if you have a complicated tax situation that affects future years. Because the IRS statute of limitations to audit a return is three or six years after the date it was filed (depending on circumstances), if you never file, the clock on the statute of limitations never starts running. If your return would have been pretty simple and does not have items that affect future years, there’s probably no point in filing now. However, if you have a complicated tax situation and items on your 2014 return that would have affected 2015 and future years, you might want to consult with a tax advisor.