Ultimately it is people BUT being able to make informed and sustainable choices is the privilege of the relatively wealthy.
Yes, I'd imagine that most if not all of the people posting in this forum have the ability to choose whether to buy something made from plastic or another more planet-friendly material but not everyone has the economic ability or the availability to make that decision.
The same thing goes with decisions about food. Yes, virtually everyone is aware on some level that highly processed trans-fat filled foods are worse for them than organic fresh vegetables, but they are also generally much cheaper. Organic and ethically farmed meat or sustainably caught seafood is also much better than things that are intensively farmed, but none of those things matter at all to someone who has multiple children that they can't afford to feed.
The same thing goes for so many other things. As an example, vegan shoes are great but usually about three times more expensive than the cheapest school shoes. Who isn't going to buy what they can afford instead of sending their kid to school with holes in their shoes and waiting a few months to be able to buy the more sustainable alternative?
It often seems to me that the sustainable choices are also on some level the more luxury choices, which isn't really the point we should be aiming for. Companies who produce sustainable products should be doing so at the most affordable prices they can, to encourage mass adoption of those products.
Isn't that the point after all? Isn't the whole purpose to make sustainable the mainstream and normal option, instead of the fashionable cool niche?
So, for those who have the freedoms to choose then I think it is the people who make uncaring purchasing decisions who are to blame, but in the case of those who don't have those freedoms it is the companies who produce the polluting and unsustainable products who are to blame.
When it comes to government I'm a bit more conflicted. I do think they should be doing a lot to ensure that industries are clean and sustainable, but I'm also not a fan of governmental over-regulation and the imposing of too many rules on societies by a government, whether they are democratically elected or not.