It's just another case of Nintendo not understanding science, like Zelda being forced to eternally give birth to herself via the "unbroken Hylia bloodline". A way of trying to "explain" an appearance of a new race in the series when all they could've said was that the Rito were there all along, just unintroduced, like with the Minish in Minish Cap, the Gorons, Kokiri, Sheikah, Gerudo and Deku Scrubs etc. in Ocarina of Time.
The Rito in BOTW are supposed to be the same Rito from Wind Waker. That's why Medoh is named after Medli, one of the landscape areas after Komali, why Rito Village's theme is Dragon Roost Island, and why they're called "Rito", for God's sakes, and not some new race name. They're the same tribe, just with a new, cooler, more realistic design. I think Nintendo's embarrassed about their former "explanation" about how the Rito "evolved". That's not how evolution works, not to mention it completely ignores how the Hylians and Gorons, etc. didn't "evolve" into things completely unsuited for the environment.
Always thought the Wind Waker Rito evolving from Zora was BS, never believed it, and I'm glad BOTW proved me right.
Laruto can still be an ancestor of Medli while being a completely separate race. It's obvious the different races of Hyrule interbreed and mixed-blood is an inevitable, scientific fact. Especially in a series like Zelda where it's supposed to go on forever.
If the Rito evolved from anything it was from birds, just as humans evolved from monkeys, and the Zora evolved from fish, etc. Seriously, not hard to figure out. I'm so happy the Rito became their own original race in Breath of the Wild alongside the other iconic races of the series. It's a sign of Nintendo getting smarter.