I don't think this fella ruined 5DS.
But people think he is kinda SILLY.
On the other hand, guy above, you shouldn't trigger if you read comments like these, they come from a bunch of nerdy, uncool thugs who are chasing a BIRD GUY that doesn't even exist, only in their imagination. They call 'bird' to a very different GENOTYPE just to confuse people. Babylonians are that way.
Crow is the reason Leo didn't get his Mark until near the end of the series. Crow was originally supposed to be turned into a Dark Signer. However, his Blackwings got popular and the higher-ups ordered the animation studio to change him into a Signer and create a dragon for him, which ruined the original plan for Leo. 5Ds was supposed to end after Dark Signer arc.
It also leads into a continuation story that involves Crow as much as possible, to the point where Akiza's role as the supposed third hero is severely reduced and people actually gets incredibly annoyed at the huge amount of terrible Blackwing cards eating up slots in real life card sets.
Wow. I honestly did not know about this history with Crow and how things got changed. I am watching 5Ds in Japanese now and the songs make it look like Leo could be the 5th Signer and I thought he was supposed to have something called life stream dragon for it. But at the same time, Crow has showed up and it hasn't shown the mark yet. Same with Godwin's vague comments.