You make a good point and I definitely understand what you're saying, though I think yoshis have come a long way since their first representations. Yoshi's Island made Yoshi the star, and showed that they have family, community, and culture. and after that I think they became more "people" than "beasts", but I suppose that's just one opinion. Mario may still ride yoshi but it's more of a partnership now. Yoshi, and his species, has since become a full-fledged character and race with his/their own abilities and personality. He may have once been just a tool but now he's an intelligent creature with his own personhood.
So basically I appreciate your point and get how you didn't like my comparison, but I think he's become way more than how you describe him, starting with when they made his race much more diverse, heroic, and interesting in Yoshi's Island and Yoshi's Story.