Not to mention that there have been research into making bioplastics[0]. Though they currently aren't as good as petroleum plastics, a push for more research and using blends can significantly reduce that dependence even more. Every step forward is still movement forward. Yes, we should be moving faster, but moving forward is better than not moving at all (or moving backwards). At the end of the day we won't be able to stop all CO2 production, but we should be able to achieve sustainable levels.

People often forget that the problem isn't producing CO2, the problem is producing too much CO2. If we have sequestration techniques (natural or man made) you can produce as much CO2 as you want as long as you have sustainable levels (which currently we need negative net production).

[0] https://en.wikipedia.org/wiki/Bioplastic