I mean, when I was fifteen most of my activism was around issues that did not directly affect me -- mostly anti-war, since there was plenty of that popping up after 9/11. But if I were writing a story about my life as a teen activist, the conflicts didn't have much to do with the, uh, conflict. Not that I wasn't sincere about my activism, but it was all stuff that was at a remove from me (and my parents are hippies), so the personal drama was about things like getting rides to protests, cuties you'd keep running into at the marches and meetings, who's getting involved with which groups and what their stance on nonviolence is...ultimately, not that much about the cause itself, which makes sense, because the cause was a thing happening elsewhere to other people. Who we cared about in the abstract, but you know, that doesn't make for a very dynamic plot.
By the time I was sixteen, I was out in high school as queer, and more of my activism became about queer issues. I was still going to anti-war demonstrations and campaigning for local NDP candidates, but if I were going to pick something to write a story about from my high school experience, I'd go with the queer stuff because the fact that it was my identity, not just my opinion, meant that I could be confronted with it at any time, and it was a lot harder to walk away and brush it off as "okay, that person sees this issue differently than me, but we can just quietly think each other is stupid and talk about other things in future," because the "issue" was me. Or I would have a great conversation with somebody where they would go on and on about how supportive they were of gay rights, and I'd be like, "yay, somebody gets it!" and then I'd bring up trans issues and they'd be like "o nope not down with that," and it was a massive disappointment, and I didn't know how much I could push back against that without losing their support.
tl;dr: personal stories are usually better stories, so I'm totally okay with activists in YA being involved in super personal causes.
SISTER MISCHIEF by Laura Goode is an excellent example of multi-issue activism in a book, with a group of characters who are affected personally by different things to different degrees.