Are you sure that he said Right Mindfulness is not that important or did he imply that mindfulness alone is not that important. Some people come to me and say Steve said this and Steve said that, and I say, "Doesn't sound like Steve. Are you sure he said that?" Mindfulness is a tool. Mindfulness is like a knife, it can be used for benefit or for harm. It is the guiding intelligence behind the knife that is most important, guiding the knife. So it is very interesting in Thai Buddhism to note that it is very rare to hear the Thais say Mindfulness without Wisdom. They usually say Sati-sampajanna or Sati-panna.
They normally do not talk about Mindfulness unless it is linked with Wisdom. If we look at the Noble Eight Fold Path we can see that Right View comes first, and then Right Intention followed by Right Speech, Right Action, Right Livelihood, Right Effort, Right Mindfulness, Right Concentration. One can have wrong mindfulness but that would mean that the preceding factors of the path were wrong. Right Mindfulness means that there is wisdom, compassion and morality guiding it, so Right Mindfulness is important.
An example of wrong mindfulness; suppose a thief wants to steal some money. They mindfully walk into the bank, mindfully crouch down, mindfully open the safe, mindfully take out the money and mindfully get out. They have a lot of concentration and mindfulness, but it was not Right Mindfulness. Right Mindfulness is defined as having the prerequisite of Right View and Right Intention. This is Right Mindfulness within the Four Foundations of Mindfulness. Without Right View it is very difficult to develop the Paramis. Mindfulness is a tool but it is not the guiding intelligence behind the tool. Right Mindfulness is very important. But we can have wrong mindfulness. Mindfulness can be used for benefit or for harm.