ETC? EV? Too Much Work..

If a workload schedule is loosely based on one's intuition, then is it bad? I often question the accuracy of those numbers when the scope of work covers hundreds of dependent tasks to be performed by multiple departments, and schedule (or do list with dates) doesn't include a plan man hours requirement (plan value) and no more monitors its progress (earned value).

A workload schedule, estimated man-hours/over time, shall be the result of resolving constraints like available head counts, reasonable work hours, tools/space etc.