Mythical and ancient zoans may be more difficult to awaken than normal zoans. One explanation Oda could use I guess.
Another one being training one's DF diligently
Lucci and Kaku specifically trained their DF in a manner that was conducive for the awakening (training in their DF's innate ecosystem and what not)
Especially knowing that lucci has much more experience with his DF than Kaku it's surprising how Kaku managed it. All Stars should have had decades worth of experience too atleast.
So it makes sense that with the required training they were able to enable it. In contrast BP's were much more reliant on their skilled specialities and intrinsic abilities related to their race
- King relying heavily on his tribal abilities ( making him claim that his Zoan with his innate abilities are BUILT DIFFERENT)
- Queen using Science to integrate versatility with wild mechanisms
- Kaido also using his racial qualities (Oni)
But you still see them having some sort of mastery over their DF in tandem with their skill
So they didn't go out of their way training em prolly you could say that its much difficult with ancient Zoans
The rest of the Beast pirates i doubt given their disposition and cockyness went out of their way to train too.