No they don't. At least not if they live in the developed world. Virtually all disposed of plastic in the US and Europe is sequestered in solid-waste landfills. Modern landfills leak virtually nothing to the outside environment.
Virtually all environmental plastic contamination comes from third world countries in Asia or Africa. In particular China, Vietnam, the Philippines and Indonesia. Due to rampant corruption and lack of oversight these countries have gross mismanagement of their solid waste disposal.
Plastic is completely fine to use. As long as it's properly disposed of, there's essentially zero environmental impact. If you live in a first world country, I can assure you that your plastic straw will absolutely not end up in a turtle's nose. The issue is that the international community needs to hold Asia and Africa accountable for not upholding global standards on ocean pollution.
[1] https://www.dumpsters.com/blog/how-do-modern-landfills-work [2] https://ourworldindata.org/plastic-pollution#mismanaged-plas...