Controversial?, but

Dan was depressed BEFORE he met Jaekyung!
I don't know y'all thought the depression would magically disappear when he left JK.
He literally said in the letter that being with JK was like fresh air (cause he didn't have to worry about bills/debt/his next meal and he had started developing feelings for the man).
When you all realise that for Kim Dan, Jaekyung isn't even close to the biggest of his problems, dude has obviously been dealing with low self-esteem/abandonment issues/loneliness and alcohol dependence BEFORE JK.
They both need to heal from stuff, but y'all are so blinded by your dislike of JK that you think you(the audience) and Dan are on the same emotional wavelength.