The situation regarding editing payware routes is not as black and white as you have painted.
Payware route creators have the right to protect their work from editing if they wish. This is done by providing the route in an encrypted form. Again, as the legal copyright holder, that is their right.
Payware routes that are not encrypted can be edited by firstly cloning them. You can then edit the clone as much as you like but the original DLC route must be present in your copy of Trainz. You can even upload your cloned route to the DLS but it can only be used by others who already own the original DLC payware route.
On the question of the number of DLC routes that are available post TS2009 I have no opinion since I am not a great user of DLC.