In some ways it's a freakish mirror of the Raimi movies. The Raimi movies set up Peter/MJ as the only love story and main emotional thread. So much so that the movie introduced Bryce Dallas Howard in the third movie (as a mix of Gwen and Ann Weying) as a rival for MJ and it just didn't work (and in fact was something Raimi was totally against). The choice to focus on the Peter/MJ as the only romance rather than do it like the comics can be justified as simply focusing on the main element and story of the continuity, whereas Peter/Gwen is a dead-end, and would never have been satisfactory unless you introduce Mary Jane and signal her as the true end-game (which by the way is how The Night Gwen Stacy Died did it, as the final panels imply).
You can't introduce a movie trilogy centered on one particular romance and then pivot to some other romance midway into the trilogy. It wouldn't work, no matter the material.
The MCU sorta did it right with introducing MJ (as she's exclusively called in the second film) as a background character but focusing on the doomed go-nowhere romance between Peter and Liz Toomes. The side-effect of that is that the MCU Spider-Man is largely not something that revolves around on romance, and romance is one of the main defining pillars of Spider-Man...and Tom Holland spends way too much time with Tony Stark and adult mentors to convincingly come off as being interested in sex.