This cannot be true, considering the superplumes of the cretaceous.
You are correct; the Earth has experienced CO2 rise of this speed before (as far as we know). But not for millions of years, and each time would have been a mass extinction event. https://earth.org/data_visualization/a-brief-history-of-co2/
Just because it's happened before (millions of years ago) doesn't mean it's not serious.
Yet, the spike in Co2 levels just after the industrial revolution is unlike any spike earth has ever had naturally. The Earth has never had this drastic changes to its climate as it had in this span of time. Earth's climate has always been changing, but the change was gradual. 200 years is just a blink of an eye in the context of a planet - changes as drastic as we observe today, have never taken place naturally before.