It's a visual distraction that makes it harder to parse a page rather than about accidentally clicking on it. Regarding clicks, advertising has often been used to carry malware and is a security risk.
I have pretty severe ADHD, and I do best on straightforward content. Turns out, most sites are rather straightforward after you strip out the advertising. It's a question of cognitive complexity.
From your response, I can tell you don't have ADHD nor understand the cognitive difficulty that comes with being offered things I do not need all the time or having to find the real content like a needle in a haystack when I have the attention span of a fruit fly.
On top of that, I'm of the philosophy that my eyes and data are not aspects of me that are for sale, as those are not things that I can easily control. I would much rather just directly pay for what I use.
Bref, I don't think Ecosia's business model is accessible, nor does it sit well with me philosophically. Just let me pay for those trees in exchange for a service, take my money, I have money!
I did not make a statement about you, I made a statement about your response. I apologize if it came off as rude, but it's clear in your response that you don't care much for accessibility (and neither does Ecosia, or most people for that matter) and don't understand what ADHD is. Whether you do have ADHD or not or do / do not care is a different topic, and is not what is being displayed here.
Besides, it's not a choice, it's a need. Ecosia is not accessible. I've been looking at Ecosia for a long time, and unfortunately I can't use it without practically stealing their server time because they won't take my money.