When fleshing out the love interest comes at the expense of the protagonist's relationships with everyone else in the movie then it's a problem. The romance with Steve is basically the only meaningful relationship Diana has other than that with the Amazons, who disappear from the movie after the first 20 minutes or so. The conflict with her mother is treated like an afterthought, the death of her aunt, who we are supposed to think of as an important mentor, has barely any impact for the rest of the movie, as everything else they get overshadowed by the romance the film decided to dedicate most of its running time to.
In the end Diana's arc revolves mostly around a romance with a man. Female empowerment much? When this got even more obvious and problematic in the sequel people were rightfully pointing it out, but in fact WW1984 was a pretty logical continuation of what they had established in the first one.
Well it didn't need to have a romance in the first place.
I'm not saying female superhero movies should never have a big focus on romance, I just think it was a poor choice for a movie they were pushing as the first female superhero blockbuster.