One thing I noticed watching the inauguration yesterday was how pervasively religious the whole thing was, in a nonsectarian kind of way; at points it felt like Biden was getting installed as a high priest of some sort, with the wreath-laying at Arlington as a quasi-sacrificial offering. Biden may or may not be a very good Catholic, but he's clearly a true believer in American civil religion, and that's honestly a relief at this point compared to the constant nothing-sacred impieties of his narcissist predecessor.
I think he is a 'good Catholic', in a septuagenarian Catholic way. Which probably is quite alien to post-war boomer Catholicism, both liberal and traditional, certainly in how it's been 'performed' in the political-public sphere since it became sufficiently 'American' enough to do so.