No, we know all the carbon used to be on the air and plants did very well indeed.
They have a tiny fraction compared to the amount of oxygen we have. Try breathing when your O2 level is as low as their CO2 is. It's amazing they survive at all, no wonder they grow so slowly.
You're waffling utter nonsense. The CO2 was in the air, it got buried, we're putting it back. Where in that is a problem?