Could anyone paraphrase this sentence for me? Thanks

I was reading "The Unbearable Bassington" by Saki, and I came across this sentence that confused me. Could anyone paraphrase the bold part for me please? Thank you so much.

I would stimulate the waning enthusiasm for Christianity in this country by
labelling it as the exclusive possession of a privileged few. If one could induce the Duchess of Pelm, for instance, to assert that the Kingdom of Heaven, as far as the British Isles are concerned, is strictly limited to herself, two of the under-gardeners at Pelmby, and, possibly, but not certainly, the Dean of Dunster, there would be an instant reshaping of the popular attitude towards religious convictions and observances. Once let the idea get about that the Christian Church is rather more exclusive than the Lawn at Ascot, and you would have a quickening of religious life such as this generation has never witnessed. But as long as the clergy and the religious organisations advertise their creed on the lines of ‘Everybody ought to believe in us: millions do,’ one can expect nothing but indifference and waning faith.”