This is a good thing.
This is from Wikipedia regarding Irreligion in the United States
"Unaffiliated Americans are sometimes referred to as the "Nones" demographic, which include atheists, agnostics or “nothing in particular”.According to Pew in 2017, 72% of the "Nones" believe in God, a higher power, or spiritual force."
The thing is "No Religion" does not mean 'no belief' in you know who, in fact Wiki says 72% on one survey were believers.
Also, on a different note. I don't think there is a reduction in religion per se, but there seems to be a reduction of the public displays of religious items and people in general seem to be less concerned with belief in god [of course there is a vocal minority, which wants to push the country in favor of its own morality]