The best thing for anyone to do is to support/organise direct political action to change our actions at a global scale. Personal initiatives can only go so far.
We have a limited time left (I apologise for not backing this with a citation but this is a rushed reply) to act, and personal sacrifices here and there won't help. Our carbon emissions are still growing overall and we need to reduce them somehow.
Also some of these points aren't entirely correct. Reusing plastic bags will probably have a lower carbon footprint than using cotton (I owe you a citation for this but it's out there). Also, there's a conflation between climate change and plastic pollution throughout - let's be precise in addressing these topics.