lol Good job imagining smoothly flowing traffic. You must not live near a major city, because lane closures on highways always devolve into the exact scenario you're attempting to ignore.

Buddy, I live in fucking Boston. They shut down a lane going into the Sumner every morning, and yeah, it's slow, but it doesn't get backed up unless some dipshit decides he doesn't want to let anyone in.

I've been stop-and-go traffic probably literally hundreds of times and that's EXACTLY how people merge: by blazing past the already stopped traffic and cram in right at the last second.

If someone is trying to merge into another lane while traveling 20 mph faster than the lane they're merging into, sure, that's unsafe. But doing that a mile before the lane ends is also unsafe. The problem you're describing is just speeding.

The assholes rushing up to the end of a closed lane when traffic is already slow ARE NOT ZIPPER MERGING. They're cutting in line.

This is what you fundamentally don't understand about the situation; you two are not in the same line. You are in line to move forward. They are in line to enter your line. When traffic in the lane that's closing is light, it might feel unfair they go in front of you, but that's just how it works. The fastest way to resolve the situation is for everyone in the open lane to let one car from the closing lane go in front of them when the lane ends.

They're further increasing traffic density,

No they aren't. Traffic density is increasing because the number of cars is remaining the same while the volume of road is reducing. Density is going to increase no matter what, but if you handle that increased density in an organized manner, like having all the cars merge at the same time (AKA a fucking zipper merge), you can reduce the slowdowns the increased density causes.

That is why rolling stops happen

Traffic waves (I assume thats what you mean, since rolling stops make no sense in this context) happen when someone experiences an unexpected traffic pattern and has to stop short, causing the person behind them to stop short, and so on. If you want to reduce traffic waves, the best thing you can do is behave as predictably as possible. Having everyone merge at a predictable time, (like, for example, at the end of a lane) is one of the best things you can do to prevent traffic waves.

people WILL slow down once density reaches a certain point, and cramming a closed lane full is INCREASING DENSITY.

Literally the opposite is true; the same number of cars spread over two lanes have a lower density than those cars spread over one lane. That's what density means; a rock has a higher density than air because it has more matter crammed into the same volume. The density of the traffic will eventually increase no matter what when the second lane ends, you’re just advocating for that to happen sooner and in a more chaotic manner because you feel like you're getting cut in line.

This isn't rocket science, yet a lot of you fuckwits are clearly still playing with crayons.

Let ye who understands the concept of density cast the first stone.