The original bacteria that were engulfed to become mitochondria are the "alternative route". It's clearly possible for a cell to have oxygen metabolism on its o

The original bacteria that were engulfed to become mitochondria are the "alternative route". It's clearly possible for a cell to have oxygen metabolism on its own because that's how we got here. So the question is, is endosymbiosis the only way to integrate that with a large, complex cell? When you phrase it that way, it should be clear which way the odds lie. But yes, "worship" is not quite the right word for whatever obsession it is that people have with mitochondria.