That's at least partially true. World population in 1850 (before the use of modern fertilizers) was about 1.6 billion. Then you have to take in account mechanization of agriculture and genetic selection of varieties, which also probably multiplied the yields several times.
But I would argue that all these practices are part of the aforementioned "traditional agriculture".
Well, mechanization is powered by oil, yes? And genetic engineering could be applied in any case.
In any event, you haven't made an argument that "traditional agriculture" is more efficient than applied ecology (Permaculture is an (the?) exemplar.)
Yield per acre is greater in a Permaculture farm than in a traditional farm, often by as much as an order of magnitude or more. Inputs are fewer too.
More importantly, under Permaculture the soil improves over time, while in traditional agriculture it is degraded and eventually becomes desert or wasteland.
A well-designed permaculture system should exceed industrial farming if you are talking about productivity per square meter. The problem is that the amount of labor required is totally unsustainable to feed billions of people.
That's where I see smart technology playing a role. Industrial agriculture involved building farming techniques around the machinery we have available. We "just" need to invert that approach and build smart machinery that enables us to glean food from highly-productive ecosystems.
> the amount of labor required is totally unsustainable to feed billions of people.
I disagree: in a well-designed system there may be a lot of labor in the beginning, but it should fall off within a year or two to a very low level, much lower than conventional farming.
(I admit a lot of "Permies" don't seem to set it up this way.)
Traditional agriculture is about the least productive way to interact with Nature.