I've been trying to tell you, Bob.
You have a chance to eat the cost on DP and NM and saving face in the long run rather than attempt to recoup costs on DP (throwing good money after bad), having it bomb, then being forced to make a hard decision on canning New Mutants after the fact.
Not only is Dark Phoenix coming off of Apocalypse (one of the worst of the X-Men movies, if you can believe that) but fans generally are anxious to see MCU X-Men. These movies performing poorly, both financially as well as critically, will hurt the X-Men brand in more ways than one and it will just make the wait even long while they give it a chance to recover.
Just look at the lukewarm reception (by Spider-Man standards) to Spider-Man: Homecoming from general audiences despite being critically well-received and fans being excited about MCU Spider-Man. Spider-Man 3 and the Amazing Spider-Man films hurt the brand and it was already 3 years after ASM2, but people were feeling tired of Spider-Man. Even ITSV, which was critically well-received and successful for it's $90M budget, made $375M worldwide, which is almost half of the similarly superhero-themed, Big Hero 6 or The Incredibles, and a fraction of The Incredibles 2 which came out the same year.
Just rip the bandaid off now, Bob, and do us all a favor. I bet even Simon Kinsberg secretly wants you to can it, despite it being his baby, his first film, something I'm sure he feels proud about in some way and wants people to see, I bet future Simon is screaming across the multiverse for you to erase it from existence so it doesn't taint his directing career before it starts and embarrasses these actors who will have to live with this stinker on their resume.