I talked to a project manager recently who was so busy fussing with the schedule (WBS) that he didn't have time to make decisions on the project. He was a project administrator, not a project manager.
If you're working on a difficult and complex project, spend time on the schedule. You need to review the critical paths (through people and tasks), and look at who's spending time where. You may even need to do this on a not-so-difficult or complex project. On the other hand, don't spend all your time on the project schedule.
If you don't have the time to review the project schedule *and* do all the project management work, hire a project administrator, someone whose job is to manage the schedule. That will free you up to do the project management, the more strategically important project work.
You can't leave the project schedule alone to wither and die. And, you can't spend all your time on the schedule with no time left for dealing with people, measuring what you need to measure, and making the inevitable tradeoff decisions.
When the schedule threatens to overwhelm you, obtain a project administrator.