Single use plastics literally don't matter if they end up in landfill. The vast majority of plastics in the ocean are coming from about 5 rivers in China. Plastic in a landfill is fine, it's a no-op: oil comes out of the ground, does not get burned into CO2 in the atmosphere and then will go and sit in the ground for several thousand years (or more likely, we'll dig it all back up once energy is cheap enough that it can depolymerized and reused).