There is zero useful evidence because there is no one to collect it.
The Institution of Civil Engineers was founded in 1818, after decades of random civil engineering societies in Britain doing the exact same thing we are now (running around like chickens with their heads cut off). It wasn't until after the ICE's Royal Charter a decade later that civil engineering began to get really systematized into the "real engineering" we know today and that charter effectively established them as a regulatory body that allowed that to happen.
I'm not sure that is entirely true. There have certainly been a few people who have attempted to study what did or didn't work in industrial settings - either pure academics or people working in industrial research labs. But I agree that currently we have nowhere near enough data to form robust conclusions about almost anything in this field and I think this is the strongest argument that the industry is not ready for any kind of licensing and regulation regime.