You sum up a fundamental problem of the world so well - you don't know, but you damn well wont let that stop you from formulating a strong opinion about it!
The stuff you tend to find washed up on beaches contains a large proportion of land-originated bits and bobs such as lighters, toothbrushes, and beach sandals, but also a large fraction of already-partly-decomposed plastic fragments, impossible to ascribe to any particular source [2].
Personally I'm not in favour of an outright ban (give me back my 100 W lightbulbs and 2000 W vacuum cleaners!) but EU-wide taxation could surely disincentivize plastic cutlery with respect to bamboo or other decomposable.
[1] https://ocean.si.edu/conservation/pollution/marine-plastics [2] "Composition and potential origin of marine debris stranded in the Western Indian Ocean on remote Alphonse Island, Seychelles" Duhec et al. Marine Pollution Bulletin 96 (2015) 76–86
Sorry, I couldn't see your healthy skepticism as it was blocked from view by your statement of fact.
In the scenario you describe, you would probably get help planning the celebration and pool items from that group. Shops would likely begin to rent out utensils and such for these sort of situations if there was a need. It's not so hard to imagine alternatives.
"With plastics accounting for around 80 percent of marine litter"
Government:
"the EU rushed through deliberations on the planned restrictions in less than a year."
Solution:
"Ban the plastic that doesn't end up in the ocean".
Good job.
Maybe someone should have told them the plastic in the ocean comes from countries without trash service, and from fishing, maybe they could have funded some charity work or NGO's or something.
This ban isn't going to help a thing.
So if I'm hosting a birthday celebration for 50 people, I'm supposed to what? Ask guests to BYOC (bring your own cutlery)? Waxed paper plates and cups work OK (although not for hot drinks), but bamboo cutlery gives me a nails-on-chalkboard feeling.