Why did the US Navy move away from depot ships?

Did skilled-trade costs and competition from civilian repair firms help push the US Navy away from depot ships?

Yes. Those personnel pressures mattered even though the capability remained useful.

Skilled trades were expensive to train and retain, and naval service competed with civilian ship-repair employers for the same expertise. Those personnel pressures helped end the US Navy's depot-ship model even though the capability remained useful. The decline therefore involved labor and retention as well as hulls and budgets. A navy must sustain the specialist workforce carried by a depot ship for the vessel to provide value.