They are quite attainable, it is just that most people don't feel the urgency of preventing an extinction event or they feel like "individual change" is more important than societal change. (Eg, Extinction Rebellion is one subgroup that does get the urgency)
They probably are unattainable, but that's only because we (an electorally significant subset anyway) opted to sit on our asses for 30 years. The Kyoto protocol (https://en.wikipedia.org/wiki/Kyoto_Protocol) was the largest international collective effort and ignored by certain selfish countries.
Every significant challenge humans have faced in history has probably felt like that.
That isn't to say we'll definitely solve the challenges facing us now. We might not. It's just that how we feel about the problem isn't actually very useful besides being good motivation to actually try.