Thunderbolt is a step backwards. It does not support DisplayPort 1.2
Just like the automobile was a step backwards because there was no way to connect your horse to it? The telephone was a step backwards because you couldn't use it to send telegrams?
Thunderbolt will do everything that DisplayPort did, plus more. DisplayPort can't do everything that can be done through Thunderbolt. They're not compatible, and that may cheese you off, but your claim that it was a step backwards is silly by any means of measuring such things.