"Could it be that all theories that do not work have one thing in common: they are obscure?"
That's part of the problem. Generally atheists consider religion-peddlers to be obscurantists. Depends on what we mean by obscure though. Some very worthwhile things do take effort to understand, but they can be understood to those who are willing to invest the time - thermodynamics, information theory, rocket science - all of them are very understandable. Each would be thought obscure by the lay person on first blush, and yet each is amenable to assimilation to the person who studies hard enough.
(Religion, otoh, epitomizes obscurantism.)
This is what Popper was trying to address. Marx and many others claimed (and continue to claim) that their ideas are "scientific" and so Popper naturally wondered "What is that makes a theory scientific?" That is called the "problem of demarcation." In the process of trying to solve this problem, he addressed the problem of induction raised by Hume centuries previously. That is, he came up with a deductive justification for science by rephrasing Hume's problem. It's a little confusing at first, but it's not THAT confusing. My daughters learned the basics of falsificationism in 7th grade. (No kidding. I was quite surprised to learn this.)
Over the millennia, the eminence of various groups have waxed and wained. Once "Knowledge" of the Cosmos rested in the minds of priests and kings. Their claim to knowledge was pretty much accepted on faith. Some things they could support, but others, they could not. With the rise of science, the priests have progressively lost standing. More people began to see the priests as the Great Oz chanting, "do not look behind the curtain."
People began - rightly or wrongly - to actually trust the results of science. Most of them don't understand it, not because they "can't" but because they're too lazy to put in the effort. But the knowledge is out there for anyone who is willing to study. The fact remains, though, that people tacitly accept "scientific" as a sort of Underwriters Laboratory seal of approval. It doesn't mean the "theory" is right, but it implies that it has been through some sort of rigorous "testing."
But the priests are jealous. Increasingly people are rejecting the old ways and the priests are losing their following. Their coffers are dwindling as is their authority. And so they are now trying to sell religion as "scientific." They put the label on it and the unwary are hoodwinked. Works for anyone trying to sell something. Nowadays all sort of products are marketed by giving them scientific sounding names: vehicles, electronics, hair products, religion. They want to associate their brand with the science label - and they are quite successful.
There have been and are many religionists, including some "intellectuals" who have promoted comically stupid ideas as scientific:
Arthur Conan Doyle promoted mediums and the existence of fairies.
He was much better about writing about logic than practicing it, as is obvious to anyone who has read Sherlock Holmes. Doyle was a brilliant writer to be able to create the illusion of logic without the substance of it.
Edgar Cayce continually used scientific-sounding, quasi-educated jargon to convey the "knowledge" he acquired in his "trances." Truly educated people would view his ramblings the same way they would the verbal acrobatics of Slip Mahoney (from the Bowery Boys).
Marx ... well, I think Popper does an adequate job of refuting him.
Various New Age enthusiasts - continually using words like "force" and "energy" among others as if the addition of this sort of verbiage adds credence to nonsensical ramblings.
Many religious obscurantists also like to promote their unique access to the "wisdom of the ages." Merlin knew things we didn't know; so did the Egyptians (pyramids have great powers!); so did the Chinese. This last one is funny. Modern anti-racists and faux multi-culturalists complain about how westerners objectify asians by spreading the view that asians are "mysterious." Of all the tripe to come out of the multi-cultural movement (and I *am* a multi-culturalist, just not in the sense of these pseudo-intellectual twits), this is the stupidest. For CENTURIES, Chinese (and other asian) cultures have promoted their mysteriousness - and NOW their bonehead descendants are pissed off that that the west bought into the blather. These are the wages of obscurantism.
