How useful are simulators in pilot training?
Flight training devices (FTD) are the non-moving, no-visuals cockpit replicas you seem to be reference as "computer simulators".  These provide a real cockpit layout (real avionics, switches, buttons, etc) that are used as procedure trainers and to learn cockpit flows.  The main purpose of these is so you are aren't wasting time in the expensive full flight simulator and can get right to work once you get in there.

Once FTD training is finished, you move into the full flight simulator (FFS, typically a level-D sim per FAA certification) which are simulators with exterior visuals and a 6-axis hydraulic motion platform.  These are the devices used for the actual flight training in airline training.  You are expected in your first sim session to already know your way around the cockpit and not be too distracted by where all the buttons you need are so you can focus on the flight training.  Being at that comfort level for the first sim session is the purpose of spending time in the FTD to start.