“Meanwhile, 37.2% of people – 22.2 million – declared they had “no religion”, the second most common response after Christian. It means that over the past 20 years the proportion of people reporting no religion.”

While the game is changing, people are walking away from it. Non-religious != non-christian as the implication of the latter is a different religion. Perhaps activities that have negative views are just not popular or desired or even relevant anymore?

the source offer better insight

https://www.ons.gov.uk/peoplepopulationandcommunity/cultural...