To be fair, carbon capture does not have to entirely offset all of global emissions to be useful, it only does if you're trying to use it as a single solution to climate change by itself. But if you were using it to augment a reduction in emissions you'd need less of it, or if you do eventually reach net zero global emissions someday, but want to slowly reduce carbon already there to bring the world back to the temperatures that used to exist, you could do so more slowly as a long term project.

I agree that the quantity is mind bogglingly big, but I think that good brainstorming starts by not shooting early ideas down, but after all the ideas are out, evaluation can begin.

Here is some general optimism jn the face of "greenwashing". I think that human knowledge is fractal, and if any human stares at a single part, they can zoom in enough to see the gaps in knowledge. And those gaps in knowledge are "low hanging fruit" for whatever profession or passion project you are in.

It's not an alternative to producing less of the damn stuff. But it can be turned into a useful material, not just stored. Ideally one that can replace, or reduce the carbon footprint of, materials like steel (~2B tons/year) and cement {~4B tons per year).

Something like this: Carbon capture process produces hydrogen and construction materials

Not necessarily exactly that, I have no idea if this one can live up to its promise. The hydrogen by-product has the potential to be extremely useful as a clean fuel but that depends on whether they can eliminate leaks during production.