That's a perfect example of gamers thinking that they know it all because they play video games. An MMO isn't launched because 10 people got together and said "Let's make a game that only we think is fun." Before a game even gets green lit, lots of market research, segmentation, and full out design documents are pitched. Look at a game design document. For DOOM it was 50 pages long. You don't create a game blindly, you have to cover almost ALL of the mechanics on paper before even starting.
That being said, this is an MMO and if you've ever worked in the industry you know that with MMOs it is impossible to make everyone happy and that it is impossible to take into consideration all the suggestions thrown on the forums. Furthermore, if you've worked in the industry you know that the forums are actually a small percentage of your playing population. The vast majority is busy playing the game instead of going to the forums.
That doesn't mean that the forum community is to be ignored, but one of the jobs of a community manager is to take in all the information, suggestions, complaints, etc and pick out the important things and present those to the dev team. That's what they are paid to do, and they do it very well considering how much this game has changed since early beta.
These threads of "change this or this game will die" or "all these things are ways this game can improve" might get looked at, but most suggestions fall on deaf ears for the entire reason that everyone has an opinion on how to make a game that THEY find enjoyable. The reality is that your suggestion does not take into consideration all the in-game and out of game effects it will have, such as how this change affects every class and every player, what resources are needed to make it happen, will it make the game enjoyable for everyone or just for a small group of people, and more.
tl;dr every MMO has people that are paid to process and dissect information from all channels, not just the forums. The intricacies of developing, let alone maintaining a healthy MMO, are unknown to most gamers because they base their expertise on games based on how many games they've played and how many hours they've put in.