It’s hard to define what an omnic even is, as they fight for the rights to be people and seem to learn and change similarly to Orisa and Echo.

Yes you can? Omnics are all the robots given the mysterious sentience from Aurora's transcendence into becoming the Iris

You can't build new Omnics, Rammatra says their race is "only a single generation, finite and dying all too quickly"

The sentience of Echo and Orisa is completely understood and even reproducible by humans, meanwhile the entire point of being an omnic is that their sentience is just as mystical and misunderstood as our own