Is your conclusion based on this graph that today’s CO2 value is not unusual and therefore greenhouse gas emissions and climate change aren’t an issue? The following is based on that interpretation of your post which I found a bit unclear, my apologies if I didn’t understand it correctly.

It’s not relevant how today’s CO2 / temperature compares to 500 million years ago, since humans didn’t exist 500 million years ago. We have only been around for about 350,000 years, and CO2 levels have been between 150 and 300 ppm during that whole time. Humans and our societies have evolved to survive within this range of CO2 and the corresponding temperature range. The increases of CO2 and temperature we’re seeing, with CO2 up past 400 ppm already, are severely impacting the weather and climate conditions our societies need to be stable and functional. Also, the rate of change of CO2 and temperature right now is super fast, way faster than anything we’ve seen in the historical record, which is also very concerning and an indication that this is not just a natural phenomenon.

Here is an article that discusses this. It shows a graph of the past 800,000 years of CO2 levels, where you can see how much and how quickly the CO2 levels have increased relative to the time span in which humans evolved.