You are not wrong. We tend to zoom in on on the wrong problems. Most of continental Europe produces a lot of waste. Almost none of that ends up in the oceans. The problem exists mostly in coastal areas with a lack of legislation and rules or just a generally a sloppy attitude to cleaning up. And shipping in international waters. Once you are in international waters, there are very little rules and essentially no enforcement. Most of the problems in our oceans come from very specific countries and shipping just dumping their waste directly in the oceans. The problem is not the oil industry but some countries not managing their waste effectively.
Of course the best thing is just not having one time use plastics to begin with. But we tend to over-emphasize the problem and focus on the wrong parts. People using e.g. straws in their drinks is maybe unnecessary but in tons of plastic it's a very minor part of the actual problem. Especially if most of it goes into the trash and ends up in a landfill or incinerator. E.g. People using plastic or paper straws in Berlin makes no measurable impact. It's all very symbolic. The Spree, the main river that runs through Berlin and the only way trash could physically make it to oceans, has been pretty clean since the DDR stopped dumping toxic waste into it a few decades ago. I don't think rule changes in recent years for one time use plastics made any measurable difference.
It's more of a problem on beaches and near coastal areas where some people can't be bothered to clean up after themselves. You see the same on public roads or train tracks where people just toss their crap out of the window. This is the root of the problem: too many people just do the wrong thing without even thinking about it.
IMHO littering fines and more effective enforcement would be very appropriate and should be fairly uncontroversial. If people are being jerks, just treat them as such. Shame them into doing the right thing. Inconvenience them. Etc. Littering is a choice. And it should have consequences. And when people know there might be consequences, they usually adapt. Other things that work are deposits on bottles and cans. Making people separate their trash.
And then go after the big polluters and force them via tariffs, trade restrictions, etc. to do better.