Give me the Death Note, I can be trusted to act rationally. The only “undeserving” to end up on it would be people who step through Metro doors and immediately stop, even though there’s people behind them.
More seriously I know the author has said it’s about power corrupting, but if that’s the story he wanted to tell then he should’ve chosen a different protagonist. Its also a silly mantra, we do not live in a Tolkien novel, power isn’t some supernatural force.
the death note being on Earth was Ryuuk’s way to have fun - and he got exactly what he wanted. its purpose was to entertain a shinobi, every benefit/drawback it caused was purely accidental