At least in terms of how soon you can get powerful ones through events?
Because from what I hear, you can get the likes of Mewtwo, Arceus, Genesect and Deoxys before you've even beaten the main game now thanks to Nintendo's online events, so you can pretty much plough straight through everything without it being able to put up a fight.
I see what you mean with badges (I've had Pokemon misobey me before), but come on, a level 100 legendary Pokemon could move once every five turns and still beat most normal opponents. For example, it doesn't matter how much time it wastes sleeping or goofing around, a level 100 Mewtwo or Arceus is going to absolutely flatten anything before about the seventh gym At minimum.
I don't use any Legendaries in the main story aside from the ones you're able to find during the game. Otherwise, I do my best not to rely on them. Do I still train them? Of course, it's awesome to have them on standby...but I don't like people who rely on them, and I do my best not to be one of those people. I think the reason they're making it easier is because of the rewards for completing the dex in recent games. Meh, personally I don't have a problem with it, but that's because I do my best not to abuse them. For those who do...well, they're depriving themselves of learning how to cope in difficult situations, which'll hurt them in the end. No skin off my back.
Generally, the only people who use them are kids who find the games too hard, or people who DO want to plow through with no troubles at all. How is that any different from Nintendo's other Super Guides?
I think of it this way the lengedary pokemons are spit in to 3 three categories.
.All important/special.also called god legends
.seeker/watcher/truth tellers.also called wondering eyes
.rare at times/maybe powerful/Protection.the hiders