Negative remarks in forums (regardless of the developer) is generally an outlet of frustration. If a program doesn't work correctly, the fault is automatically assumed to be the developer. A little at-home attempt at problem isolation usually results in solution or at least understanding.
It would be ideal if a soft-synth would work right out of the box with any operating system on any computer through any DAW and sound processor and be operated by any MIDI or USB controller.
Unfortunately, universal compatability isn't even possible within mankind so why should it be expected in anything man creates? The devleopers do the best that they can, realising the purpose of the company (to make money) and dealing with time-lines (to keep the money coming in).
There have been VAST improvements in soft-synths over the past few years, a lot of that being due to negative comments in forums and developers paying attention to that feedback. Granted there is a degree of senseless whining by those who won't seek to resolve their own issues, but even those complaints result in more user-friendly (dummy-safe) software.
The bottom line is: If the software is working correctly, no one complains about it. They're too busy creating music. Those that offer remarks, both positive AND negative, contribute to better software and, hopefully better music which is the goal we should ALL be aspiring to.
Peace,
Dave