Translation:People are boring.
Don't let Duo get bored, otherwise we'll all get sucked into a hellish dimension
지루하다 is "boring" while 재미없다 is "not interesting". You could technically use them interchangeably.
Not exactly. 지루하다 refers to the atmosphere or the experience. For example, my history class is boring. 저의 역사 수업이 지루해요.
재미없다 refers to the object itself. For example, history is boring. 역사가 재미없습니다.
These are just learning examples, they don't need to make sense necessarly all the time.
지루하다 is boring.. how to say the people are bored? Boring and Bored mean 2 different things...
"심심하다" would work, and "지루하다" can be used for both cases:
그것은 지루합니다. It is boring.
나는 그것이 지루합니다. To me, it is boring.
나는 지루합니다. I am bored. / I am boring.
The subject is omitted in the last example if it means "I am bored."
심심하다 talks more about your feeling, like when you're feeling happy or sad. It's more of an emotion.
지루하다 talks more about the experience of something, like when your class is boring.