It really Is sad regarding DD. I’m a fan of both actors, but to some people in the fandom, Gillian can do no wrong whilst David is some sort of sex-addicted penniless actor who desperately needs the Mulder role.

It is very sad, and it’s also very untrue. David doesn’t need money. A simple research on Google would show those people that he is worth a few more millions than Gillian. After the X-FIles, he managed to be a lead actor and a producer on a show that lasted seven years and which ratings and international sales worked very very well. He literally created himself a brand new fandom for Californication. He wrote two books which both ended up with great reviews from the New York Times and if I’m not mistaken were also both bestsellers. 
He’s going to self-produce Bucky Fucking Dent as a movie this year, because he happens to have the money (his words), and he’s living his best life and touring all around the world with his music. David Duchovny doesn’t need anyone’s pity and if he doesn’t want to say goodbye to Mulder it’s because he loves this character, he loves the series, he loves working with the crew and most of all, he knows already what it feels like to quit this character. 
I don’t think I need to pinpoint that Gillian’s career outside The X-Files is a bit less successful so far, money-wise at least.