Obviously it matters how much co2 is in the atmosphere.
Discussion
Correct, when there is very little, life on earth would die out. If we were back in the 3000-8000 ppm range, life would likely explode again.
This is actually the sort of thing I'm talking about, you feel the need to have some caveat here, when there is absolutely no evidence that CO2 is bad for anything in any levels that are even practically achievable or have ever existed since there has been life on the planet at all. Every reasonable piece of evidence we have says that more CO2 means more life.
https://primal.net/e/nevent1qqsve5gl5ufrfhw6y8wtwu0qumj8cesmclxxcvttem2t70k7mkfwnmczp2k5z
Actually it matters more how fast things change. Biological systems can’t adjust to rapid changes because evolution takes many generations. There are upper limits and lower limits that humans and most other things can’t survive, but there are rates of changes that will destabilize our world regardless of our ability to survive within the absolute values.