How is something critical if it has been transgressed and we are still alive? Or on the very first moment every single one is past we all suddenly die?
The passengers weren't all affected equally either. A lot of first-class passengers made it onto lifeboats, whereas third class passengers mostly didn't.
(The analogy breaks down a little in that we don't have lifeboats and the collapse of our ecosystems probably won't be as absolute and catestrophic as a ship sinking. The Earth's ability to sustain large numbers of humans may decline significantly though, and a lot of things we take for granted now may be gone.)