Speaking as someone who's worked in a position very similar to GM Deynger here - they're absolutely right, feedback does get read and passed along from the community to the higher ups. Collecting feedback is a big part of that type of position. Why else do you think there would be GMs directly interacting with the community? The issue lies in whether SEGA JP is willing to listen to that feedback or not, but I sincerely believe the NA GMs and support staff are doing their best. So please continue to give feedback on the game, as that's the only way anyone's voices can be heard. If nothing else please don't spread the false impression that feedback is outright ignored, because that kind of defeatist philosophy doesn't help anyone at all.
Change won't always come quickly and sometimes there are other factors involved that might not be obvious from a player's perspective, but as long as the NA staff can point at feedback and say "look, our players over here don't like this, here's proof that this is still a problem", there's still hope that the higher ups at SEGA will listen. If you want to see the game improve and be the best it can be, you need to speak up, and you need to do it in a way that the NA staff can easily show it to their bosses at SEGA. Long, angry rants about how the game is terrible aren't going to be taken seriously by higher ups even if the points are valid. A calm explanation about why X part of the game isn't good and how it can be fixed, submitted through proper channels, is a hell of a lot easier to pass along successfully.