Yep. Actually meeting most of the straw hats is an extremely low bar yet somehow Yamao hasn't passed it.
People love to talk about how Luffy's all that matters when it comes to joining the crew, which is both right and wrong. Technically, as the captain ultimately the final decision is Luffy's. But straw hats aren't just a collection of individuals. They're treated like a family. When a new member joins, they not just getting hired by Luffy to do a job. They're a friend to the group that they want to officially bring into their family and that's what the toasts are there to celebrate.
You'll notice that Oda always makes sure to have the future nakama interact with the whole crew at some point. Outside of Luffy, they generally develop a notable relationship with a couple of them in particular, but they're always familiar to the group as a whole. Oda's had plenty of time to do the same for Yamao, yet instead of developing her with straw hats, all the time was spent on her relationship with Shinobu and Momo.
After she split up from protecting them and ran to the top to fight Kaido, she literally had to run past each and every different floor which all the straw hats were on. Oda didn't bother have her interact with a single one. Previously, the only straw hat she met for about 5 seconds was Franky, and that seems far more for the sake of setting up his fight against Sasaki than anything.
Forget nakama...heck, forget friend too. As of now Yamao is a total stranger to the crew.
Having a conversation with Luffy and also having their own dedicated arc where they are the main character is far more important than interacting with everyone in the crew. The arc a potential straw hat is introduced is the best chance where a potential straw hat gets character development and bonding with Luffy.
its funny how you say that meeting every straw hat is a low bar that Yamato hasn't accomplished yet, well if it was a low bar to begin with then it probably wasn't all that important in the first place. Then that means that there are more important things required in becoming a Straw Hat- its not the be all end all. Not to mention that Yamato will most likely get it done by the end of the arc anyway.
Going by your logic, Sanji should have never joined the crew because he never talked to Zoro after he joined, the two only talked directly to each other for the first time after Baratie in the Arlong Park Arc when Sanji confronted Zoro for the first time for Zoro accusing Nami as a traitor. Why did Sanji still join the crew?
Jinbe's never talked to Zoro directly either. And in Wano, Jinbe still refers to Zoro in a formal way by his full name Roronoa Zoro. Why did Jinbe still join the crew?
More important things like being a main character in the arc, and also having the 1 on 1 talk with Luffy, are things that Yamato has that Carrot doesn't.
Besides, I've never seen Carrot ever talk to Robin, even now-so much for the importance of character interaction.
Your argument that: a potential straw hat must meet all of the straw hats and interact with them in order for them to join and its non-negotiable, is a inconsistent and flawed requirement if not every straw hat who joined followed that pattern in the first place.
Meeting most of the straw hats isn't only a extremely low bar, its also a inconsistent and inconsequential one.