I think Piety has become extremely situational. I had a moderately wide Mayan empire (7 cities on a small map) and I made it work. I used Mosques and Holy Warriors and went through Piety. Organized Religion gave me 14 more faith per turn, so that was decent. I was able to build wonders in 6 out of my 7 cities, so Reformation was helpful. I ended up winning handily in pretty much every respect, so it was fine.
The biggest problem I have with Piety is that it seems confused. It wants to help religion, which works well for wide; if you go wide, however, you're usually not picking up too many wonders, especially in multiple cities. I had to cater my play around the tree and overall, didn't feel that I was getting any great benefits like I'd get from other trees, namely Rationalism. I didn't once put a Holy Site down, nor was I making enough happiness or gpt for Mandate of Heaven or Theocracy to be worth it.
As others have said, I've actually gone Rationalism for cultural victories to keep up in tech just to get some key wonders (ET, SOH, etc.). I've actually won a culture victory going Tradition, Liberty, Honor, Commerce, and Freedom. I'd say that it's no longer a handicap to you if you don't choose it for culture victories.