That's their belief, but.... How much "dislike" is there among fans for Scott Franzke? Now I'll grant you, Scott's only on radio. But radio listeners probably skew older than the average fan (teenager: "What's a radio?"); radio listeners probably represent hard-core fans (who else is going to listen to Phils broadcasts on radio all these years?). I would argue that radio listeners are more familiar with Harry (and Whitey) than the typical current TV watching fan... and as a group, we don't dislike Scott Franzke - we just wish he could do TV and radio at the same time!
Scott Graham, IMHO, was the post-Harry "whipping boy" - disliked by many fans because he wasn't Harry, and yet tried to project a distinctive personality (and was undercut by Wheels in internal politics, as well). McCarthy became something of an anti-Graham - as in, no particular personality, just bland. Heck, he served to make Wheels seem less than atrocious, which wasn't easy.
Just to throw out some related comments: I'm OK with Ben Davis. Decent voice, doesn't seem to try to be a know-it-all (Wheels). I think he can grow into the job. Kruk, I'm ambivalent. He can be funny, but I think like most "character actors," he's best with limited exposure. Murphy isn't bad at play-by-play (when he's used there), but as far as I'm concerned, they can just scrap the "sideline reporter" stuff - it's apparently there to placate the casual fans who want "entertainment," as opposed to baseball, on TV.