People are disappointed that Zoro didn't learn more from the samurai? That is to be expected. It was a sword place and he's a sword guy. There are some swordsmen themes at play though in that arc.
For example, Zoro was considered a criminal right away because a guy killing people with a sword framed him. This is a samurai theme because Mr. Bushido got framed for being the very thing Bushido principles abhor which is a samurai without a code.When Zoro was brought to trial, he found the real killer and delivered justice to him.
Another example is Oden's fight with Kaido. He fell victim to subterfuge which is something samurai don't use in duels. It is considered cheating and the code of honor samurai follow doesn't permit it. Kaido had a sense of honor as well which led him to being upset with someone interfering in a fight and he recalled what happened to Oden back then in his fight with Luffy. Then he took his anger out on the Cipher Pol guy.
During his duel with Kyoshiro/Denjiro, Zoro was called a Ronin. Do you know what a Ronin is? It's an outlaw samurai who has no master often living in disgrace and obscurity. It's also an insult that classifies someone as a lesser samurai. Interestingly, in modern times, it is used to describe unemployed salarymen and highschool students who haven't gone to college or university yet. It's another name for a NEET (not in employment, education, or training).
You were hoping the samurai would have imparted their knowledge to Zoro and some especially strong sword users would show up with cool new abilities even elemental kinds. That expectation may not have been met. Though, I think many things a person learns as a swordsmen is something they learn on their own anyway. The type of knowledge he would find actually useful would be mystical in nature and inaccessible because it is esoteric.
I do understand the disappointment. I'm still disappointed that we didn't see them do much with the sea-stone there. What did they do? Like 1 nail, and some handcuffs? That sucks lol