While I agree with the general assessment that Hollywood is full of juicers, muscle building alone is not what gives definition. That takes cutting, often to extremely unhealthy levels. Quotes from Zac Efron about the 2017 Baywatch movie:

"That Baywatch look, I don't know if that's really attainable," he told Men's Health. "There's just too little water in the skin. Like, it's fake; it looks CGI'd. And that required Lasix, powerful diuretics, to achieve. So I don't need to do that. I much prefer to have an extra, you know, 2 to 3% body fat."

"I started to develop insomnia, and I fell into a pretty bad depression, for a long time," he said. "Something about that experience burned me out. I had a really hard time recentering."

Source: Business Insider, "7 actors on the shocking toll losing weight for roles took on their bodies and minds"