if you don't code yourself, then you probably don't have any idea how much time and effort is required to implement your 'improvements', and/or perhaps your suggestions really aren't very good to start with, therefore annoying the dev, who spend perhaps months or years creating his end product, only to have some random guy from the Internets post 'suggestions' that come off as criticism.
This is largely irrelevant to the OP's question - do the other users who are outright rejecting the idea of adding new features code? Do they touch the codebase for the app in question? All end-user feedback is useful at some level, it's useful for developers to know how people are using their software and even if just one report isn't enough motivation to add a new feature, if this is requested a number of times it might point to worthwhile future development, or changing the workflow in the software to accomodate the way the software is used by other people.
Asking for a new feature or function in software isn't criticism - in fact, it's the complete opposite. It's showing the developer that you use the software enough to care to provide feedback and you're thinking about ways that the software could potentially be even more useful.