So, yeah, the Titans offense is not a very good offense (currently 25th in scoring), but that should not take away from the shutout.
The Titans scored 43 points in their Week 1 victory over the floundering Browns (with one defensive TD, but they have scored 55 total points over five games since - including twice being held to 7 points (by the Bills and Jaguars) before Broncos shut them out.
So yes, their offense can be shut down, but this defense has come a long way since getting torched by the quick passing game of the Raiders and the running game of the Jags.