Itachi is the reason Oro is underrated. People somehow correlate with being vulnerable to Sharingan genjutsu with being weak... it's not like the vast majority of the shinobi world would fall prey to it.Ppl don't realize how powerful Oro is bc we haven't really saw his all out fight. We only saw Armless orochimaru's fights and against Hiruzen he used Edos, he did almost nothing and most immportant thing is that he was joking around in all of his fights.(except maybe Itachi)
But he is really powerful. Just like how you mentioned, he played with 4T Naruto despite his body rejecting him which strains him massively. Kusanagi, Shirohebi no Chikara, Juinjutsu and Triple Rashomon etc. alongside powerful, large reserves of chakra make him very dangerous.