The reason I think you could say Yanni does have talent, despite making music that most of us don't like, is that he's not trying to make music that we would like. He's trying to reach a mass audience of mostly women, who are seeking romantic, emotional, superficial compositions that are "uplifting" and "nice" and "beautiful." The music isn't meant to be complex, or shaded, or difficult, or subtle. That would actually detract from the appeal for most of his listeners.
So, who knows whether Yanni is capable of doing work that is more complex or interesting, if he wanted to. We're judging him harshly because his work is like a poor, lame cousin to the music of Kitaro or Jean-Michel Jarre, but I really don't think Yanni ever meant to be anything other than popular.