I think masturbation is harmless and don't mean to be a nofap type person who thinks it gives super powers.
Some anecdotes of mine:
But I think porn can lead to issues such as giving people unrealistic expectations for what an adult's body should look like, male or female.
I remember watching a video of a nofap guy and one thing he mentioned was being unable to maintain an erection or reach orgasm once he had a girlfriend, and how part of it was he couldn't feel arousal anymore without certain types of content. I used to post on a forum where some male members talked about giving up porn, and how after a few weeks of abstaining they felt arousal at more normal things like thighs.
Another time I saw a woman's ass get posted on a forum, some members called it "gross" because it was normal looking. She was a normal weight and everything, it just wasn't a hyper attractive BBL gym butt. A lot of photos edit out small bits of cellulite that 90%+ of women develop regardless of weight, blemishes around the genitalia get covered up in porn by putting makeup over it, etc.
I don't know how harmful to say this is but it would be sad to have your expectations of sex and people's bodies ruined by how they're portrayed in fiction.