Everyone can make some positive change. It doesn't have to be perfect. It just needs to move the needle, and in doing so we can unlock the next layer of feasible actions.
To be clear, I do think everyone is capable of making positive change in this way but just 'moving the needle' isn't nearly enough and I don't see why we can't simultaneously push for a very sensible carbon tax and additional environmental protections.
Especially since the biggest polluting companies are so big because everyone buys from them and there are not many alternatives. Saying the problem is that we are buying from these companies seems as much a "darn consumers, amirite?" shrug.
Point is- we should do both. But expecting all consumers to be able to make an informed choice about the entire ecological effects of every product is not possible when there often isn't information or a choice. Especially since under the current system companies are actively incentives to pollute as much as possible since they don't pay the cost of cleanup, and to lie about it with glitzy ads and campaigns.