While I can see the potential distractions, I haven't found it TOO hard to remain reasonably focused.
Spoiler
The raiders in Lexington slowed me down so that I wasn't rush to Diamond City as quickly as I'd like. I wandered over to Boston Common/Goodneighbor area at about level 12 but got spooked by all the super-mutants running around on the way so I had a reasonably in character reason for putting off that part of my quest. Once I got to the point where supermutants were reasonably routine enemies I rescued Valentine and ran straight through killing Kellogg and extracting his memories. And now I have another reasonable in-character reason for slowing down: the daunting prospect of searching the Glowing Sea.