How can CO2 be 36-million times stronger on Earth than on Venus?

Back in 1978, when I first heard about the CO2 theory of climate, people introduced the idea by talking about the planet Venus. They said, look at how Venus’  atmosphere is full of CO2, and look how Venus is 445 degrees hotter than Earth.  It must be from a greenhouse effect they said.

Lets do the math about this idea that the entire greenhouse theory edifice was founded upon: Venus’ atmosphere is 92 times as dense as Earth’s, and it is 96.5% CO2. Meanwhile Earth’s atmosphere is only ±400ppm (parts per million or 0.04%) CO2.

So Venus doesn’t just have a little bit more CO2 in its atmosphere. By volume it has around 221,950 times as much CO2 as Earth (92×0.965/0.0004=221,950). And Venus is ±445°C hotter than Earth. So for each degree Venus is hotter than Earth, it has 499 times as much CO2 (221,950÷445=498.8).

Now back on Earth, CO2 levels were around 175ppm (parts-per-million) at the bottom of the last ice-age, and until the 1970s they were ±333ppm. And 175ppm is just over 1-in-6,000 — and 333ppm is 2-in-6,000.

According to the ice core climate data, this 1-in-6,000 change in CO2 levels corresponds to a 12°C change in Antarctic temperatures.  So on Earth, each degree hotter corresponds to a tiny 1-in-72,000 change in CO2 levels (1/6,000÷12°C). Comparing the two planets:

On Venus 499 times more CO2 = 1°C
On Earth 1/72,000th more CO2 = 1°C
500 x 72,000 = 36,000,000

How can CO2 be 36-million times stronger on Earth than on Venus? And doesn’t such a huge discrepancy in the supposed power of CO2 disprove the greenhouse gas theory of climate all by itself?