For me this question is a bit too vague (not knocking the OP as I like the topic) but it depends on what stage you are in with the series for me. If it's a new series and you're getting a first sequel I would say go for refinement all the way to improve upon what they made but to also define the series.
However when it came to the Zelda I think Breath of the Wild was the perfectly innovative title for that franchise at the time. I'm personally someone who wants to see Zelda go to its more traditional dungeon crawler roots again but I cannot deny that they needed to shake up the franchise.
If i was forced to answer the question above I would probably say innovate to any long-standing series but for young franchises refinement is far more important.







