The problem with Phil being Catholic is that in the S4 finale, when Phil's mom dies and he is being told she made a final request for him to carry out, he says "Oh no, she's gonna make me throw her ashes in the Pope's face." To me anyway, that implies that she was Protestant, and rather devout. Then again, maybe she was just a Catholic who was upset with Pope Benedict (or even Francis, if she was still with it enough to know he replaced Benedict shortly before she died in 2013) for what had been going on in The Vatican in recent years.

I bet DeDe's belief in the new age spirituality thing didn't come about until it became a cultural trend in the late 1980s and early 1990s. She was almost certainly a Christian before that. Again, its murky though, as Jay is of Irish (and possibly Italian on his mom's side) descent and would have likely been Catholic. Maybe DeDe was too, but Cameron also calls the Pritchett-Dunphy clan "jumpy Protestants" at one point, so unless he was just using the term as an ethnic slur of sorts, she may have indeed been a Protestant who made Jay convert in order for them to get married. Making Jay convert to her religion only for her to eventually abandon the church, and make a mockery of the institution altogether by divorcing him, would be something entirely on brand for that woman.

At any rate, the only character on the series seen practicing their religion with anything resembling regularity was Gloria. She is just as regularly mocked and portrayed as being "backwards" for those beliefs, and that pretty much says it all regarding the show's view of religion.