At some point in the early 2000s fandom crossed over from being primarily rooted in a speculative fiction concept of furries, which required some kind of scientifically plausible origin (they were genetically engineered, they were aliens, there was some kind of convergent evolution, etc) to 'my character looks this way because I like how it looks'... to add to the chorus here in the comments, I felt that shark OCs were the most striking indicator of this change: no one was pretending they had evolved into that shape; their anatomy was fantastical and not only was that fine, but it was unnecessary to devote mental energy to why they look that way.
(this is furries as opposed to toons, of course <3)
In fandom there's always been a tension between what different people consider to be 'realistic' attributes, but what seemed to happen around this time was that fans generally became less interested in contemplating that question; expressing themselves through their original characters took priority.
