Is this opinion on personal computer flight simulators too strict or is it actually true?
It isn't true, not as an indictment of the simulator software community as a whole anyway. It may be that your pilot friend doesn't have experience with modern simulators, let's take X-Plane for example...

X-Plane has a "professional use" version, which is simply the regular X-Plane with a commercial license and a few extra features. The underlying software is still the same. X-Plane "for professional use" can be FAA certified as a training device. 

This means that the aircraft behaves exactly as would be found in the real world. In fact, X-Plane is sometimes used to verify flight models before more expensive methods are used, and they are relatively accurate. NASA has even written research tools to utilize X-Plane. X-Plane's Garmin G-1000 is incredibly realistic, and X-Plane "for professional use" can drive G-1000 simulator devices. 

You can buy other "professional level" simulators for home use like the Redbird Jay which runs the same FAA approved software as the certified simulators. The same is true with Elite Simulator.