but 3 different writers without a plan?

Five, actually. TFA has three credited writers and RoS has two, although Abrams is one of each. For comparison the OT had three and the PT had two, and all the of the first six films at least gave Lucas a story by credit, so there was guiding vision. RoS gives that credit to DotF’s writers (for some reason), so if you count those the ST has a whopping seven different writers, only one of which appeared for more than one entry (Abrams). Compare that to the PT being almost singlehandedly written by Lucas (with help on AotC) and the difference is night and day. The PT knew what story it wanted to tell and the ST didn’t. Hell, the ST even had a different producer each on top of Kennedy and Abrams (the latter only for the ones he directed).