Can I assume you are also opposed to straw and plastic bag bans? Unlike tree planting which at least does something, those bans are almost entirely worthless.
Bans on straws and plastic bags have a direct measurable impact on local marine wildlife and in the reduction of microplastics.
Now that Asian countries are introducing bans, we should start seeing slowing microplastic accumulation. Within a decade microplastic accumulation should peak. By then we'll have more efficient means of addressing microplastic pollution.
One point not often brought up is that microplastics in the ocean contribute to ocean temperature rise, since the plastics are able to retain (and thus radiate) more thermal energy. This one of the reasons the great garbage patches are hypoxic--warmer water holds less oxygen.