I took the "dumb actor" remark to mean that Frid screwed up and didn't capitalize on his fame the way he could have. The Halls separately made comments to the effect that Frid was probably sorry he didn't take the second DS movie. I don't believe that decision was the last minute though, Gothick; the reason for the Halls' displeasure seemed to be tied to the fact that Frid was a cash cow and the biggest draw. Removing himself from the project hurt in the pocketbook and in terms of visibility. In the Halls' place, I would be sorely disappointed.
Another point is that there are people who say an actor is a "bad actor" because he/she can't walk and chew gum at the same time in front of the camera. Working in front of the camera doesn't just require good acting skills but technical skills as well. Frid didn't have those technical skills. Does that make him a bad actor? For people who believe a good actor is also a technical actor, yes.
I suppose the litmus test is to try and decide why so many people remember the character of Barnabas Collins 40 years later . . . because of his long teeth? Pointy bangs?
What makes me remember JF is his presence; the way he completely took over every scene. He ruled over scenes with all his fellow actors. As Barnabas, he won the heart of Liz, the respect of Mrs Johnson and Roger, the admiration of Vicky, Carolyn, and David, and the hatred of Burke Devlin. He made us dread Willie's every waking moment, he made us adore history, and he had a fine sense of dressing. JF's scenes with Grayson Hall are a tribute to two fine actors. They made their scenes come to life, I think, because they cared about their roles on the series. And not just for the bread. I think they portrayed their characters the way they did because they had a sense of respect for one another, a love of the characters they portrayed.
That's my take on it anyway.