A concrete counterexample: plantura.garden is a large, reputable German-language gardening magazine / brand, and probably exactly the kind of legitimate site one would expect on .garden.
So while the abuse numbers may well justify treating newly registered / low-reputation .garden domains with suspicion, blanket-blocking the entire TLD seems like it would create real collateral damage.
Nice. Check out https://github.com/meodai/color-names for a rather large (29888!) collection of hand picked colors in case you want to expand your project.
No. Their only purpose is to act as a kind of receipt: "look, I actually really did waste all this energy".
The solution to the puzzle itself is irrelevant - it's an operation that would be extremely simple but that's made very, very hard on purpose. And the sole purpose is to align incentives by using lots of energy.
So while the abuse numbers may well justify treating newly registered / low-reputation .garden domains with suspicion, blanket-blocking the entire TLD seems like it would create real collateral damage.