Firstly, Reducing CO2 levels requires a small amount of sacrifice and minor inconveniences; both of which, while they can be overcome with relative ease are too much to ask.
Secondly, it would also reduce, and possibly redistribute, the net worth of people who have more than enough for multiple lifetimes, and that just wouldn't be right.
So as you can see, there really isn't anything that can be done.
I meant, let’s say an alien civilization has great tech, but they use a lot of energy and thereby a lot of excess heat. Could they not lower their co2 levels and possibly even dim the sun a little to balance things out? As in using a Dyson swarm
They'd lose more in solar potential than heat they'd save by blocking the sun - sunlight is a very useful form of energy, and you don't want the planet getting too cold either. Engineering the heat balance by changing the atmosphere, the ground or adding devoted heat exchangers like were discussed elsewhere would help a bit, but not infinitely.
If they want to keep building more, they need to go to space, and yeah, that leads to a Dyson swarm pretty fast. And then on to other stars. In the really long term there's more than enough space and matter for one intelligent species; the main currency is time until the universe ends.