Should atheists take the Shroud of Turin seriously?

Well no its not testable.

The “process” changed the C14 , people who collected the material didn’t notice the invisible seam between old and new, the acid burn isn’t actually acid burn,
its not really testable…

There’s a difference between “not testable” and “we are capable of making up lies that let us pretend we have a reason to ignore the results of the test”.