True. Especially if nature already has the best direct carbon capture technology since hundreds millions of years for free: trees!
Trees are cheap but need a lot of space and water. People are cutting down forests because they want to use the space for something else.
Ocean surface algae also collect solar power and carbon, and there is little demand for ocean surface for other uses. Algae are limited by available trace minerals -- cheap ones.
The only one ongoing I know of is Sahara dust being (naturally) blown out to the Atlantic ocean. Otherwise, just talk. Somebody who did an experiment had his results suppressed, crudely, with a false narrative promoted in its place. Why that was seen as necessary, and how it happened, seem even more interesting than the experiment.