All you say is true. Life will be fine. Earth has been much hotter with much more CO2. More CO2 will improve plant growth. And we eat plants so that part is a good thing.

But humans evolved while CO2 was below 400ppm - the last time it was that high, 20 million years ago, there were no humans. We kind of got used to 280ppm.

I'm not saying we can't tolerate it (our speciality is standing upright, sweating, and persistance hunting which means we excel when it is hot... if we go back to the old ways). I'm not saying we cannot adapt (we will build sea walls, people will migrate, a bunch of cold tundra will become livable for the first time).

All I'm saying is this: IF it turns out that the consequences end up sucking for some reason that we did or did not expect (e.g. massively violent storms that no human has ever witnessed, huge unpredictable climate fluctuations that make crop planning nearly impossible, etc), THEN we cannot go backwards, we will just have to live with it for a thousand years.

Because the basic physics of drawing down CO2 are so fundamental that no technological innovation is going to do better than plants already do. And that's no where near as fast as we are emitting it.

Any hopes of a technological innovation in this regard IMHO is a fairy tale. It's not quite as impossible as faster-than-light travel, going backwards in time, or perpetual motion machines, but it is nearly as impractical as humans flying around in jet ships like the Jetsons, costing far more energy to draw down than to emit.

NOTE: I didn't do any research for this post, this is off the top of my head. I may have said something wrong. This was a best effort reply.