The photographer's eye and brain are the important parts - the camera is just a tool. The results are predictable once you've run a roll or two through a new one (I have two and they aren't the same). You just have to know what scene and what lighting will work. And for some reason, Holga shots frequently work well on lith (see gallery here for examples, there are many from others way better than I).
Of course there are pros using Holgas. If we know their names is up to their marketing. Whether a print sells to people other than other photographers is entirely due to the results, not the camera. A buyer doesn't usually say, "I will/won't buy that because they didn't use X camera."
At least one of mine is quite sharp in the middle (or can be), but it's nicely OOF at the edges (barn shot shows it well). And, yes, I have a Hasselblad and I use it for different results.
If you're going to drive off-road, you take the Durango, not the Mustang. When the need for speed kicks in, you want the Mustang. It's all about having the right tool for the job at the right time.