This is only true because the Senate's floor time is valuable enough that leadership would rather move on to consider other bills than waste time on a real filibuster. The "silent filibuster" is not an official part of Senate rules.
People have been saying that Congress is gridlocked and ineffective, and that is true, by several subjective and objective measures. But even in the gridlocked state there are still a bunch of bills that are debated and passed. And it takes floor time to work on those.