To be fair, some improvements have been made, even at the feet of these giants, driven by government action and populist initiatives. This has been at the cost of concentration and increases in pollution and poverty in the poorest nations. The future looks bleak today, as the divide grows and progressive progress has all but halted.
Billions didn't.
USSR census population in 1989 was only 286 million total, while the Holodomor and the Cambodian genocide combined were between 4.4-8 million.
And the Holodomor (and broader famine in the rest of the USSR) looks suspiciously similar to the failure mode of the British government with the Irish potato famine and the Indian famines under British rule, each of which played a part in those people wanting independence, as does the Chinese great leap forward's 15-55 million.
Even with those, and the Chinese famine happened so soon into a transition away from agrarian society that to me it seems more like a tragedy than a consequence, it's still not billions.
No, what saved billions from starvation is fertiliser, and policies of subsidising over-production so that the bad harvest years food is merely expensive rather than insufficient.
If it was "capitalism", then the Lassiez faire British empire wouldn't have had the Irish potato famine nor would the East India Company have been in charge for so many famines in India.