I don't see people ridiculing the fact that a child disappeared. I see people ridiculing some of the ridiculous theories which have been proposed to explain that disappearance.
My problem with the German authorities is that they seem to have found their suspect by listening to various informants, then set out to find evidence of his involvement. Some years on, they still don't appear to have found enough to lay charges. His previous convictions, although they suggest he could be the perpetrator, are not evidence that he was involved.
I think your problem with the German investigation is that the prime suspect is called Brueckner and very specifically not McCann.
Brueckner, the German prime suspect was first suggested to the Germans in 2013 by Scotland Yard.
It has been said by Amaral that the Policia Judiciaria had also investigated Brueckner in the early days of Madeleine's disappearance.
Although police may have suspicions or are merely eliminating individuals in the process of investigating a crime it is not considered appropriate to take action against them without evidence.
As a result of international appeals for information made by Madeleine's parents on the tenth anniversary of her disappearance people came forward with evidence and some people came forward with faked up photographs.
So ACTING ON INFORMATION RECIEVED (a well known way of cracking criminal cases) the German police investigated Brueckner and found sufficient evidence to opine that tragically Madeleine is dead and that Brueckner is the prime suspect in her murder.
But you do know all that already ~ sigh!