Yes and no.
First, the truth is that if you were spending hours every day outdoors with the sun on your skin (like our ancestors did), then you probably don’t need a red/NIR light device.
But since most of us do not spend hours a day with the sun on our body, we end up deficient in the nutrient of red/NIR light. So getting a red/NIR light treatment will be supplementary.
Having said that, sun has benefits that red/NIR light does not have. The sun emits UV light, which we use for several purposes, like synthesizing vitamin D. It’s also going to be better for setting circadian rhythm in the morning.
But red/NIR lights also have some advantages over the sun.
One is convenience and access. Not everyone lives in a place that is sunny all year-round. And not everyone has the ability to get outdoors in the sun every day during the time of day where it’s warm and sunny.
In addition, for very targeted treatments of specific issues, the sun is not going to give you the precision targeting of a light device that you can shine specifically on the thyroid gland or on a specific wound site with the precise light intensity and dose that will lead to the best effects.
Also, the spectrum differs in important ways that affect some goals. In particular, for skin anti-aging (on the face for example), many people would want to avoid getting lots of UV on their face from the sun (which may accelerate skin damage and skin aging), but get the benefits of red/NIR. The sun doesn’t give you the ability to do this—with the sun, you get the whole spectrum of red, near-infrared, far-infrared, blue, and UV. But with a red/NIR light, you can get the therapeutic benefits on your skin while avoiding the potentially counterproductive wavelengths entirely.
To be clear, red/NIR light devices are not a replacement for sunlight. We still need plenty of sun exposure to be healthy. But red/NIR light devices can make up for our lack of sun exposure and give us several targeted benefits in a way that we cannot get from the sun.