But what if man’s ability to create a collective dream with others can carry on even after our biological bodies are gone.

This breaks down already at "collective dream", in two ways. Dreaming may feel like you're perceiving some alternate reality. but even inside your head that's not how it works. There's the ongoing mental process of imagining it. And there isn't some underlying "if it were real" that you're looking into, what you imagine is driven by what's ever going on in your head at that moment.

For example, pro-LGBT Christians imagine pride-parade Jesus and anti-LGBT Christians imagine no-gay-wedding-cakes Jesus, both reflecting how they feel about the issue. Then as the demographics shift and anti-LGBT Christians come around to realizing gays are just people, they start imagining pride-parade Jesus. Point is even inside their heads there never was a Jesus they were imagining, there is a the process of them projecting whatever they feel at the moment onto an imaginary moral authority that agrees with them. And the result doesn't have some concrete hypothetical virtual reality to it, it's as shifting and contradictory and momentary as the emotions that drive the process of imagining Jesus.

And the "collective" part is just as much of an illusion. Religions have a strong component of affiliation, which is a social concept, and everyone in the religion imagines they're talking about the same thing, but again that's not how it works. Back to the previous example, take an issue and both sides imagine a Jesus who agrees with them and think the other side is "getting Jesus wrong" and "they aren't real Christians". The dream isn't collective, there's again a process -- this time a social process -- involving affiliation and authority and agreement and disagreement and all kinds of stuff like that. Even when there's a degree of consensus among a particular religious grouping, that doesn't create a "collective dream" with some external existence, it's just some degree of social consensus.

Anyway that's even before you get to the bosh about this stuff continuing to exist in some sense after the people involved have died. It didn't even exist when they were alive. It's just people, distinct people, and what's going on in their heads, which is about how they feel at the moment.