At the same time, they also said that they have too many people applying right now. In this case, the cost of taking someone else's spot seems pretty significant. I'm not sure I'm above-average important.

But your point is taken; I might apply anyway.

A person close to me is intending to donate a bunch of money to atmosfair, which is a german environmental charity. I pointed out that this might be suboptimal and so she instructed me to find out what a better option would be.

Is there anything like a consensus on what the most effective environmental charities are that someone can briefly point to? Alternatively, feel free to just give me your own opinion.

The goal as I understand it is pretty much just to reduce CO2 emissions. (The charity does this thing where you donate a particular amount to offset the CO2 that got into the atmosphere because of a flight you've taken.)