If the ocean can really get rid of plastics in 5-8 months we should throw all our plastic trash there.
It won't get rid of all of it, but most of the flaoting stuff breaks down quickly with direct UV exposure in the salt environment.
Ideally, it should be recycled where feasible. Landfilling i the next best option, and no, we are not running out of landfill space, and likely won't for thousands of years.