I really enjoyed WWE for a time ~ 1999-2000 when the Rock was one of the main characters. He had a ton of charisma and talent that was obvious. He sold all his 1-liners and schticks and bravado very well - the crowd loved it and I can still vividly remember some of the stuff he said.
I think that all translated over to being a credible actor in Hollywood films.
Gronk's charismatic but he never once has struck me as someone who has any kind of range to sell to Hollywood.
I'm not an expert at all on acting, but I think if Gronk thinks he can do what the Rock has done, he's been sold a bill of goods.
Then again, Hollywood couldn't care less about his acting abilities if people buy tickets to see him on screen.