That's a matter of opinion, there's plenty of talk that Polaris was meant to be much better than what it was, but it didn't meet expectations so they just had to go with what they had.
Most likely that was because of the 14nm process not being mature enough yet. We saw the difference with the RX 580s using a mature 14nm process and being able to consistently achieve 1400MHz boost clocks and overclock to 1500MHz on the regular compared to the RX 480s.