I would say a relevant part of them comes from individuals. If you believe the issue is important enough, then raising awareness is the right direction so they take healthier choices. However most of the worlds population lives in developing countries, and microplastics are very low in their list of priorities, their top priority is actually making to the end of the month with enough food, shelter and some medical care or even education for them or their kids.
Blaming everything on greedy corporations is a very superficial analysis.
This is why we, as a population, won't agree to curb CO2 sufficiently to address climate change but instead will simply adjust and, maybe eventually, accept geoengineering based approaches. That said, the next 10 years will be telling in how conservatives react to much higher home owner's insurance premiums...