It can be, but it's fairly easy to swamp yourself with API script stuff.The learning curve for Roll20 is fairly shallow...
Roll20 is kinda like GURPS. Start with the baseline basic base stuff and then add things on slowly until you reach your level of saturation.
(My level of Roll20 experience: I ran several games on Roll20 for about 4 years.)
I thought Roll20 was excellent. But FOR ME, I found the level of automation and the work flow of Fantasy Grounds to be more to my liking. And we could never get the integrated Voice to work anywhere near consistently.