Quite the opposite, it barely burns in an open fire.

Most of it melts and gets everywhere hence the projectiles. The flame created from it is not very strong nor clean burning, which means lots of smoke but not really a lot of heat.

Not to mention burning plastic releases a crap ton of toxic chemicals into the air which can easily damage your lungs.

Besides thin one use plastics like bags which generate microplastics, most of it is actually better off buried in a land fill, believe it or not.

Plastic would be easier to recycle if specific types were enforced and easy to sort, but there's so many different types and proprietary materials available that it's not currently feasible.

China even did it for a while with cheap labor but they only did it because they had a high demand for all raw materials so anything to produce plastic was approved.

Like I said, you can try throwing a plastic bottle into a campfire and see what happens. It's not a pretty sight.