Plastic pollution is bad, but it's different (and orders of magnitude more manageable) than the pollution that is causing climate change.
"Greenhouse gas emissions from the plastic lifecycle threaten the ability of the global community to keep global temperature rise below 1.5°C. By 2050, the greenhouse gas emissions from plastic could reach over 56 gigatons—10-13 percent of the entire remaining carbon budget. "
- https://www.ciel.org/wp-content/uploads/2019/05/Plastic-and-...
For reference, the two plastic plants mentioned in the article you linked can emit 3.65 million tons of CO2 per year (about 30% of the nations plastic production annual total). This is a little less than what the average natural gas power plant produces in a year.
And there are about 1000 gas plants in the US. And gas is the least emissive of the power fossil fuels.
So while strictly speaking plastic production does create greenhouse gases, you can basically offset an entire years worth of plastic production emissions with only a handful of wind and solar farms displacing fossil fuel power plants.
Also I don't count burning plastic in lifecycle assessments. That is trivial to outlaw and dramatically pumps emissions figures.
Nope, not true. Easy to say you can regulate the heck out of enforcing it, but if it was easy it would have been done long ago. Besides there not being a feasible and cost-effective way to track all the plastic in circulation, trust people would be quick to protest about government overreach on their right to pollute