Allied races and world design go with the story. Those are planned out YEARS in advance. Game mechanics, the major ones, are also planned out well in advance. So if they want to revamp the crafting system, they would start that way before the expansion where the changes happen.
Smaller gameplay changes such as tweaks to the systems they have selected for that expansion happen during development, internal testing, Alpha, Beta, and even after release in patches.
Yes, it does matter. However, the impact is often not felt for years after the feedback is given due to the way the game is developed and planned. An allied race for example is NOT a simple thing to do. It has to be proposed, lore sorted, stories written, quests written, char model made, art assets and armor made, etc. Getting all that approved, funded, scheduled, staffed, and integrated into the game is not a fast thing.
There are tons of examples though of Blizz listening to player feedback - we did get flying back after all, even if Pathfinder was a compromise. It is just that a LOT of the feedback is so conflicting. For the vocal folks who want X class change, there are vocal folks who want Y instead. For those who want a PvP focus, there are lots who want PvE, or Transmog, or Raid or… it goes on and on.
Backing up and looking at it top down, examining the development timeline, and focusing on what you can have an impact on, and when, helps reduce frustration.
For most big things it is going to be “considered in a future expansion”.