Honestly its not "darkness" or anything that has not led the X-Men films to do $1 billion at the box office like the Marvel films. Its the fact Marvel spent time building a Universe of films to a bigger payoff as we saw. Iron Man and others didn't start landing that massive box office til things grew that way. The X-Men films were part of solo sequels and had no real team building to a universe.
Its not til now that Fox realized they had a treasure trove of X-Men characters they can mine. Like Deadpool , X-Force , X-Men , New Mutants and Gambit. But from 2000 to 2015 the only films released were X-Men and Wolverine films. With no real connections. (And even now Fox can't seem to connect the films that well to build the universe ala what Marvel has done).
"The story so far: As usual, Ginger and I are engaged in our quest to find out what the hell is going on and save humanity from my nemesis, some bastard who is presumably responsible." - Sir Digby Chicken Caesar.
“ Well hell just froze over. Because CM Punk is back in the WWE.” - Jcogginsa.
“You can take the boy outta the mom’s basement, but you can’t take the mom’s basement outta the boy!” - LA Knight.
"Revel in What You Are." Bray Wyatt.
That and because the market today is vastly different than what it was in the early and mid-2000s.
X2 and X3 sold around as much tickets as Spider-Man: Homecoming according to Box Office Mojos.
https://www.boxofficemojo.com/genres...st_yr=1&p=.htm
Spider-Man: Homecoming: 37,418,200
X-Men: The Last Stand: 35,780,500
X2: X-Men United: 35,646,700
Inflation in tickets prices, 3D, and the growth of the international market is the reason why Homecoming made twice as much money. So if the market back than was like it is today the first two X-Men sequels would have made 800 million.
Kevin Feige does credit the marketing team at Disney.
https://mobile.twitter.com/Kevfeige/...57546386231298
So homosexuality is "dark" and falls into the same category as "bloody, brain blown out, frontal nudity, kinky sex, cursing and body dismemberment"? Good to know.
Anyway, the way you're describing it makes Fox's X-Men look like a whole franchise of Tarantino movies, and it's definitely not like that.
Since Avengers 4 is set 5 years after the last film and Spider-Man: Far From Home seems to be set in set in present day it’s safe to say that the MCU is getting a soft-reboot similar to DOFP.