I like Yellow's design, not only is her design still freaking adorable, her design by Mato undoubtedly represents so much of Satoshi Tajiri's design philosophy of the original Pokemon games really well, intentional or not. One of the reasons why Satoshi praised Pokemon GO is because it reminded of his childhood of going outside to collect bugs. This carried over into the original Pokemon games where you see so many of the adults wearing uniforms, business suits and other worker outfits while most of the kids wore country or sporty clothing representing the outdoors that they enjoy. We can see this reflected into the protagonists actually. The original Krys sported a more sportier look before she was given a more fashionable makeover in Gen 4. The original May sported a more sportier look before she was given a more fashionable makeover in Gen 6 and then you begin to realize that the newer character designs of the Pokemon games are including a more fashionable take on Pokemon characters rather than the usual country/sportier take that represents kids having an adventure of the outdoors.
So with that said, Yellow's design is without a doubt the most Pokemon-esque character design there is for an character outside of the games. She sports a Strawhat, country-like clothes, boots and a fishing rod which represents Satoshi Tajiri's design pihlosophy and his childhood quite well. It's because of this I always thought the anime-exclusive characters, Jessie, Jame & Meowth looked out-of-place at the time due to how highly fashionable they looked during Gen 1 whereas I actually mistook Yellow as a legit character from the video games. I like Yellow's design, it really captures the heart of what helps make Pokemon feel like an adventure and is definitely one character I hope to not just see in an anime adaptation of Pokemon Adventures but just in the games canon because she would fit right in and I bet new Pokemon fans wouldn't be able to tell that she's originally from the manga unless you tell them.