Dear Christopher.
Agree with your early analysis regarding well-meaning figures. If their message was twisted by nasty people who misunderstood, then that wasn't their fault. They don't even deny the physical world; they merely say that it's a lower level of manifestation.
It's not the period that we need to get back to, but we can be inspired by the old ideas as we move to the future – I call this a reunification of science and religion. I therefore disagree with you that “any such universal truths in world religions lies ahead of us, not behind”. Many people in modern times have found meaning in the ancient wisdom – although ironically sometimes such thinking is called New-Agey – and they are exactly the sort of people that you want us to evolve towards.
“The more modern the society, the more free and awakened are its people”. Really? There seems to be a new wave of authoritarianism spreading at the moment. And as for awakening, there seems to be a strong drift in Western society towards atheism, secularism, scientism – the delusions that Traditionalism (in a modern, reborn form) could save us from. As the old religions say, most people are in a state of sleep, and need to awaken. (Remember Plato's cave. Only one of the prisoners managed to escape. And what a terrible time he had when he tried to persuade the others.)