people can slag off on AllTrails all they want, but it's always given me everything i need. if i was doing lots of off-trail stuff, or deep backcountry, there are better apps. but most of what i'm doing is trail running and keeping to established trails. i can make up my own maps on AllTrails and organize them easily. i tried Gaia too, and the maps on there didn't have any extra details or layers that I would need that AllTrails doesn't. but making my own maps on AllTrails was easier, and organizing them, building alternate route sections, etc was never as easy or possible in the Gaia app.
the distance and elevation tracking is accurate enough (and i rely more on my Garmin for that anyway). AllTrails has a huge user base, and that's really useful for finding reviews of certain trails, and trail conditions - the more users, the more likely a certain trail will have some recent reviews and conditions reports.
sure, some of the trails people have uploaded on the app are pretty wonky, but you can usually tell from reviews and ratings if somebody uploaded a crap route. and you can modify it to something more reasonable if you want. on the other hand, i've discovered a number of trails and locations through the app i wouldn't have found on my own otherwise.
but hey, AllTrails is popular, so it's got to be terrible, right?