The final last ditch defense of the religious apologist, when all else fails, is often the functionalist argument, that a useful lie or myth is needed to hold society together and make it civilized.

There are of course, to my mind, and probably your too, lots of things wrong with that, not least that if you need a myth or lie, then there are certainly better ones than religion. Even if you don't see a distinction between religious lies and honest but unsupported belief. ( The difference being that honest beliefs do not pretend to be supported by faked evidence. ) And that, the useful lie idea, is generally the view of the snob and narcissist who sees the rest of society as a threat to themselves, to be opposed, rather than a community to be assisted.

But perhaps the biggest problem with the useful lie idea, and is I think is worth considering. Is that simply. You have to get people to believe it. To do which you have to create an environment, in which, lies and myths can thrive, flourish and survive. Which means you have to suppress education, debate, science, healthy sceptical thinking, and well founded contradictory knowledge at the very least, as well as normalizing and making respectable half truth. And when you do that, you create thereby, a cultural environment, which not only favours your lie or myth, however good and harmless that may be, but all other possible lies and myths as well. So that a society which is set up to believe that, for example, the “golden rule” is a gift directly from god, which may not seem so dangerous an idea in itself. Is also a society where the defenses against, racial superiority, fascism, ultra-nationalism, conspiracy theories and a hundred and one other stupidities all the way down to Q-Anon, are lowered, and where there probably exist a ready made infrastructure for the promotion of falsehood, whether that be a corrupted news media, a million pulpits or perhaps both and more.

The world will always be somewhat favourable to lies, there is no prefect world, but you simply can not create a world which where you deliberately set out to promote so called, good lies, without making it a world which is also much more friendly to the bad ones as well.