No it isn't.
Her vanishing nearly half a decade ago has nothing to do with their personalities that look like they were already established long before the incident, or her birth.
Unfortunately yes it does. In the first months, no it wouldn't. Even if the parents were the prime suspects, even if someone had seen them throw a body into a river they'd still spend a lot of money dredging the river and searching for the body in hope she was alive.
Right now, years later, their character and their story is entirely relevant to how you persue the case. Unless they had an IRON CLAD alibi, like, they were at dinner, at a filmed event, with the local chief of police and the kid was seen being taken home with the nanny they they ARE SUSPECTS.
If say Greebo's list is true, sorry but it sounds horrible, they've seemingly done everything they could to hamper the investigation into their own missing child, innocent people rarely do that.
Investigations aren't free, people are paying for it, people have paid for it already and at some point its just money down a drain. Maddie was young enough that she could be somewhere, completely happy with a new family and never remember the old family.
Its very hard to find a missing kid, when the kid is openly out in some part of a world with people she considers her own family.
Or she could be dead, maybe a kidnapper killed her, or the parents, who knows, at this point throwing money into a fire would be as useful in finding her.
If she's found, at this point, it will be because someone raids a peado's "lair", and her identity is checked after looking a bit like her. THe trail is so cold its a joke.
At this stage we're funding a couple of very, strange parents who did very little to help find their daughter at the time, come across as guilty and are traveling the world, living in hotels, on other peoples money.
Everything I've seen, every interview, their strange behaviour and their seeming press hounding makes me feel like they are guilty. Suggesting we ignore them as suspects and spend limitless money to find a kid that money WILL NOT FIND at this stage, is daft.
Half the world thinks they did it, take a freaking lie detector test rather than refuse, its not hard, every step theres been things they could do to help their case, and they've refused, and each time in doing so seemingly helped waste time and effort that could have been spent finding their kid. Their own time and the cops looking into the parents.
The two potentially only suspects continue to act strangely, be evasive and refuse to help themselves, if that shouldn't effect how you persue the case I really don't know what should.
At this stage the most likely source of finding out where Maddie is, is the parents.