You don't notice that you apply your playstyle, do you? Demos limit base building, yes.
Your solution is, that obviously you think 7D2D is a tower defense and the demos brake this pure tower defense gameplay.... But 7d2d is not a pure tower defense, nor a pure FPS. But you want to change the game like you personally would prefer it.
They way you are complaining is the pure definition of SUBJECTIVE.
And like always those discussion end up at "i like to play this way, so change this in that way" and "but i like to play different, so change it in the exact opposite way". You reached that point already some posts ago. Average intelligent people conclude: There is no game mechanic possible, that suits every playstyle best. Less intelligent people still think, "every possible playstyle" is like they play the game and still discussing how to make them game without mods best for "every" player.
Besides the already thousands of threads that complained about the demolishers. Repeating it over and over doesn't help, i'm sure TFP noticed that many people don't like the demos. Your personal WHINING is not required anymore. Your analysis is not constructive, but highly subjective. Even less construcitve because you just WHINE and haven't made a single suggestion on how it could be made better.