If they did say that everything is set in stone then the "Suggestions & Ideas" board would have no purpose. So, of course they are looking for suggestions but some of the community voiced ideas just don't cut it and will not be added to the server, you can't expect them to add everyone's ideas onto the server or else there would be chaos.
I'm not really understanding your point. Are you saying that there is a lack of freedom on the server? I can understand you to an extent but with two huge worlds and regenerating resource worlds (The Mining World, Nether and End), many plugins to enhance your survival experience (such as mcMMO, the auction and Towny) I believe there is a huge amount of freedom as you can do many things on the server. Fair enough there is slight restrictions on being able to build as you either have to buy a plot in a town or spend Noobz on chunks in the Wilderness world (which from my knowledge doesn't seem to cost extensively) to get lots of land, even then you may be limited to your expansion if someone else decides to build near you but I strongly believe there is a lot of freedom on the server.
