Yes, TNT run was a fun game and, I believe, it was quite popular.
Sadly, those beautiful classic games like TNT run won't work in the new Arcade update. Furthermore, TNT run can be found on other servers. CubeCraft is focusing on a new direction and on the future with the goal of attracting new members.
Are you aware that TNT run has been incorporated into Spleef Layers?
I actually like this feature in one way because I play more TNT run now than I otherwise would have when it was a standalone game.
However, I do understand where you and many other people are coming from because, while they have incorporated TNT run into Spleef Layers, it's not to the same extent as it was when it was a standalone game... not to mention the scores that many die hard TNT run fans worked so hard to achieve. I really do feel for those people.
All we can do is to look to the future and hope that a bit more of a balance can be brought about where we can still have many of these classic games reinstated, provided it is feasible. Only time will tell. But for the time being, I get the feeling that Cube staff is working on future games that will fit into the new updated Arcade system, which may or may not involves adding back some of those games, especially some of them like TNT run, which has already been incorporated into Spleef Layers.