I don't think like that, and nobody thinks like that.
The first target before we think about getting back to preindustrial levels, is to get to net zero by 2050. If you start measuring things against a goal that's too distant in the future, you just give up.
Ok, if we talk net zero, then the what does it take the US to do that? The US is not the entire globe. Currently the US emits about 6.34 gigatons of CO2-equivalent and absorbs about 754 megatons for a net of 5.59 gigatons CO2e [1]. The emissions from natural gas power generation are at 743 megatons [2]. If we could eliminate all other emissions except for the ones from the natural gas power plants, we'd already be slightly net negative. If we could keep the existing natural gas power plants, but run them only as peaker plants, we'd be well into negative territory.
You are saying that 754 megatons is not sustainable without some program of carbon sequestration. I pointed out that 14 years ago the US consumed 187 million m3 of solid wood, which is of the order of 187 megatons of CO2 sequestration. Or about 25% of the annual CO2 absorption by all the US forests and grasslands. To me that sounds like a pretty huge rotation speed, and certainly sustainable in the long run.
> by contrast, direct air capture followed by injection into the crust where carbonatation of olivine and similar minerals sequesters the carbon is a plausible plan
It's a plausible plan, but that's about it. The facts on the ground are that we don't do it for some reason. Most likely there are some serious obstacles. Which ones, I don't know. But I know that lots of things that look plausible on paper don't look so good in practice.
The same with synfuels. Where are they? Yes, there are startups, I know about the HN startup Prometheus. But for the time being, it's all pie in the sky. How much synfuel is being produced now? The wikipedia page [3] does not seem to be very up to date, which is a bad sign in itself, it means nothing of note has happened lately. But they quote a worldwide capacity of 240000 barrels per day. You can compare that with the crude oil production of 80 million bpd. And of course, that worldwide capacity of 240k bpd is mostly high carbon intensity. The low carbon intensity fraction of that is probably negligible.
The fact that Germany used the Fischer-Tropsch process in WW2 is not that relevant. Yes, it shows the technology exists, but it doesn't show it is economical in the current market conditions. And something that's not profitable is not getting built. And once it gets built, you always need to ask yourself, how long will it take us to go from where we are to where we want to be. How long does it take you to go from 1000 bpd to 100000000 bpd? Is it years, decades, or centuries? Do we see the current growth rate to allow us to create even some optimistic predictions that we'll get to some meaningful number in a few decades? If not, then there's no reason to be optimist.
[1] https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas...
[2] https://www.eia.gov/tools/faqs/faq.php?id=77&t=11
[3] https://en.wikipedia.org/wiki/Synthetic_fuel_commercializati...