The comment I replied to was cynicism rather than skepticism.
I think the $10T or whatever outlandish figure that proponents of carbon-recapture technology plan to spend would be better spent on a land trust on which native plants would be cultivated. $10T will buy an enormous amount of land upon which billions of trees can grow.
If it were actually $10T in public funds that people are proposing to develop carbon capture technology (it isn't, but it is irrelevant whether or not it is), then I would certainly vote in favor of another $10T to buy land and plant trees.
Money really isn't the relevant constraint here. The constraints to carbon capture are, in my view, the same as any other climate technology: public and private will, land availability, and energy. That's in order of most to least intractable.
The global economy could easily absorb $20T of public funding for the DAC + billions of trees plan from now to 2050, if there were the political will for it. But of course, there isn't.
But if there were, the constraint would then be the trade-off between land use to plant the trees vs. solar arrays for the energy to power the DAC machines. But one really nice thing about DAC is that it may not have much constraint with respect to location, so it may be possible to put it in places with plentiful energy that can't easily be used in other ways. (This is not true of land for billions of trees.)
But the will thing really is the biggest constraint, and it's why I'm an "all of the above" advocate. There are lots of great solutions to this problem that you can wishcraft about executing if you were the unchallenged emperor of the world, but there is no path to an authoritarian global hegemon who uses their power to plant billions of trees. And even if there were, frankly I think global authoritarianism would be a worse outcome for humanity (and the environment) than our current climate change trajectory.
So there's no point daydreaming about some perfect "if we would only do this one thing!" solution and getting all frustrated and cynical about how it isn't going to happen because people are too selfish or stupid or whatever. That's letting perfect be the enemy of good. The solution to this will be a cobbled together coalition of a bunch of different stuff - both policy and technology - that people and governments are willing to do.
And you may retort, as many do, "no, that won't be the solution, there just won't be a solution, we're doomed!". And you may be right about that. And I may even have joined the cynical doomer contingent, if it weren't for all the herculean effort at invention over the last half a century having already put us on a much better trajectory than anyone thought we would be on at this point. We're not so far off from being able to beat this thing, we have almost all the technology we need, and a ton of people interested in attacking the problem from different angles both for selfless, but importantly also now for selfish reasons.
It will be good if wealthy and well-run oil companies begin to see a bigger upside in carbon-negative technologies rather than carbon positive ones. Very annoying from a karma / spite perspective, but good from a solving-the-problem perspective.
I don't disagree at all that billions of trees would be an excellent "technology" for this, but it's just naive to put all your eggs in that one not-gonna-happen basket, and it's childish to throw up your hands in frustration that it isn't going to happen and become cynical about other technologies.