According to the scriptures, this would not seem to be true. One of the most famous of the teachers who supposedly just uses awareness was Mahasi Sayadaw. Many people think he taught to just use awareness. However, in one of his books he encourages people to do protection meditations before one does the practice. And protection meditations happen to include Reflection on Death, Reflection on the impurities of the body, Lovingkindness meditation and Reflection on the qualities of the Buddha.
Protection meditations protect us. In my opinion, they protect us because they start to transform our view, and get our mindfulness more in line with Right View. In the scriptures, in the Satipattana Sutta, Reflection meditation was taught. How is one going to apply a perception if one doesn't think? Such as when one sees a dead body, and the Buddha says to apply this perception to our own body, "Verily, also, my own body is of the same nature, such it will become and will not escape from it." I think that's thinking isn't it? Wise thinking.
There's a difference between just thinking and Reflection/contemplation. Contemplation is directed thought. Within the forty subjects of meditation that the Buddha gave us, there are a lot of Reflection type meditations. I think he had some purpose in giving these Reflection meditations, and they help with, from my understanding of the practice, they help with the development of Right View, Right Thinking.
Mindfulness by itself is not enough. Simple example of this, is if a person is a thief, has a great deal of awareness and concentration, they've been doing it for years and years, so they can mindfully walk into a place, mindfully with a great deal of concentration, probably more mindfulness than us, and more concentration, crouch down, being aware of the body, and mindfully with a lot of concentration and mindfulness open the safe and steal the money. And mindfully walk out. However Mindfulness is not enough, because this person doesn't have Right View and Right Intention.
So there's many ways to develop Right View and Right Thought. It often depends on how we're looking deeply into things. If we're looking deeply into things with a lot of wrong view and wrong intention, we may not see anything clearly. Mindfulness has to be linked to Right View and Right Thought to be Right Mindfulness in the teaching of the Buddha. As well, there are a lot of teachers in Thailand who say the opposite, that we have to develop Right Thinking, and we can't use just awareness. So there are many views and opinions about this. Due to the fact that there are a lot of wise Reflection meditations taught by the Buddha in the scriptures, I would more incline to the view that Reflection meditations are very beneficial for developing Wisdom.