The problem with environmental sustainability is that it's complex, and not many people know that much about it at the detailed level. This means that it is a breeding ground for misunderstanding.
Take for example a bottle of Shampoo. Ask someone what the biggest environmental impact of that product is and the majority of people will say the packaging- probably because that is the tangible item that they can touch and see, and that they have to physically dispose of (ideally by recycling but often as rubbish) once all the shampoo is used up.
The most commonly recognised way to assess the environmental impact of something is to measure it's contribution to climate change. This is done by a process called Life Cycle Analysis ( which takes the whole product life into account- from ingredients, to product manufacture, distribution, sales, use and disposal) that looks at how much climate change gas is generated by the product. Because climate change potential is measured in "Carbon Dioxide equivalent" this is often referred to as a carbon footprint.
So lets consider the shampoo... and remember most people say they think packaging is the biggest environmental impact of shampoo...
The Ingredients of the shampoo are responsible for about 2% of the impact
Manufacturing and Distribution combined are also about 2% of the impact
Packaging is about 3% of the impact
What about the missing 93%? Well that's almost all down to the energy used to heat the water to wash your hair with!

If YOU were to turn the temperature of your shower down 1 degree, or reduce the water you use while washing your hair by at little as one twentieth (much more if you get into the habit of turning the shower off while you lather), you will make a greater benefit for the environment than eliminating the bottle (but manufacturers of shampoo are doing their bit, by constantly looking at ways to lightweight their bottles!)