I've seen good reviews on the Gh5II. To call a camera that improved on the GH5, which for years was a favorite, a failure is not accurate. Not everyone wants or can afford to spend $2.000, $3000 or more buying cameras and lenses. There is a lower end market. The problem for Panasonic and others is the iPhone.
I am not saying GH-5II is a bad camera (although its auto focus is still crap) but that it hasn't generated much in terms of sales. And, to paraphrase Lily Tomlin, "this isn't the art of photography".