Switzerland (well, at least Geneva and cantons around it) doesn't even separate plastic waste apart from few very specific plastic bottles. For the rest, just put it into general garbage, no false feeling of helping planet when in reality doing the opposite.
One can't really suspect swiss to be lazy or cheap on anything, in contrary. I don't know details about general waste lifecycle here but it seems other places could take some inspiration and focus energy and resources on more sane parts of waste processing.
If you assume the that the plastic production happens regardless and look at the end outcomes for the already-created plastic, i would say yes. But in that context, recycling could (in theory) reduce the demand for further plastic production so it's still better.
Still, if we're looking at comparative effort for GHG reduction, I agree in principle that landfilled plastic might as well be considered nearly carbon neutral: extracting oil, creating plastic, then landfilling the plastic is a "closed loop" in the sense that the carbon starts in the ground and ends in the ground (minus waste in the intermediate processes, of course). It's not "sustainable" because we don't have infinite oil, but it's not going to be the primary cause for climate change.
This is in contrast to using fossil fuels for energy and transportation, wherein we extract oil/gas from the earth and then burn it to transform into heat, electricity, or kinetic energy for your car. In all of these, the carbon's end state is in the atmosphere, which is worse than a landfill.
To that end, I would much rather spend effort tackling petrol cars, oil and gas heated homes, and fossil fuel power plants. Plastic is an ugly problem, but not the worst problem.
If it was coming from the atmosphere and not underground, I could see the analogy. Currently it starts from oil that’s already”captured” in this sense.