Why don't I like scriptwriting?

 Because it marginalises what I'm good at and highlights what I'm bad at. Some of the best aspects of my writing are how I control my writings pacing and rhythm. But in script, the actors and production largely control those. It's not that I have no control; In fact, both my successful scripts successfully use restraint and silence to force the rhythm down where it needs to be and gives the actors more control over it where rhythm is less important.  As for pacing - controlling pacing in script is a different beast from controlling it in other writing genres, so its just a matter of learning a new skill set I don't currently have. 

As for how script highlights my weaknesses; I've always considered myself subpar at writing characters. Now, It's not characterisation that I have problems with, but dialogue. I just struggle to make something that sounds both naturalistic and good to listen to, while also having to at every turn consider what each character wants and is feeling and why they say what they say. It just all goes over my head a bit, so writing passable dialogue means lots and lots of drafting and editing. And if I want it to be GOOD dialogue... then that's even more of a hassle.