It'd never happen in any way faithful to the series, anyway. They'd age up the kids to like 17 automatically, they'd basically have to to get past the ratings board, and it'd be pretty neutered thematically.
I'd rather they just not do it. It was what, 53 books from memory? Yeah, about a third of those were "filler" that you could skip over, but you've still got what, 30-something stories that advance the plot in pretty significant ways, that you wouldn't want omitted. You start mixing & matching, combining arcs for time reasons, and it's going to suck.
Thing is, this wasn't Harry Potter in terms of being tailor made for movie adaptations. It wasn't Goosebumps in that sweet spot of tone of "scary by kid's standards, but still suitable for kids".
This was a series with a 16 year old kid intentionally mass-murdering unarmed prisoners, of a kid having to send his cousin to kill his brother, of an orphan kid trapped in a hawk's body and struggling with the mental stuff of having to rip mice's guts out just to survive. A series with bloody Vietnam style guerrila war waged by a bunch of 13 year olds, slaves, major PTSD, pretty graphic bloody descriptions of hand-to-hand combat - with tigers & bears against sentient reptiles with razor blade ivory things coming out of their arms & legs. The authors have said over the years they're pretty shocked they got away with it, and that's just with the written word - translate that to a visual medium and everyone's going to freak.
It's like...Super 8, if it were as violent as the Cameron Terminator films, a pretty specific era/cultural setting, and this weird tonal balance where kids using alien tech to turn into various animals to wage war against brain-enslaving slug aliens doesn't come off as ridiculous.
And yeah, it's dozens of books long as opposed to the usual 5, 6, 7 tops that these Y.A. things are. With a way more controversial tone than any of these other Y.A. series. Also not sure the whole "paranoia" & insidious shadowy threat tone plays so well now, given everyone basically lives all that day to day with terrorism - the books are very, very Bill Clinton era "we're safe at home, at least" America, you'd probably want to set it late 90s too. No cell phones for the kids, internet's still pretty basic, America's at peace and stuff.
We'd get it done really sanitized & safe, if it happens. Best to not go there. The author's other (pretty great) work, Everworld and Gone, is even more intense. Basically - Hunger Games & Maze Runner, Animorphs wasn't. There's a line, when it comes to producers, censors, and parents. Even ignoring the violence and big gritty war-and-repercussions themes, a lot of the dialogue from Marco & Rachel alone would pretty much be considered "problematic microaggressions" or whatever now, it wouldn't fly.
They'd basically have to Enders' Game this thing pretty extremely, for a movie. And that wasn't even a terrible film, but it was pretty clearly sanitized & kids-gloved.
EDIT:
Thread made me curious to google image Animorphs out of pure nostalgia - remember really hating a lot of the cover art, but the hand-drawn stuff from the Chronicles books is pretty badass, and closer to the text descriptions. Love that one.
This fan art is pretty sweet too.