A friend of mine postulated that most monsters are just 'chupacabras' - meaning that they are simply things that leap out at you and try to kill you, and have no more 'story' to them than would an angry wolf.
Like, most every demon just wants to tear you apart. They just have different powers. A bulette isn't going to have a complex narrative related to its motives. A chimera, or a golem, or a skeleton, or a purple worm, or a troll. They're all just physical threats.
Monsters only really get interesting, in my view, if they create a story that affects the characters. If you could swap the monster for a golem and the story would run the same, I'd prefer something else. I usually find people more compelling foes than chupacabras. Something you can talk to, someone that has motivations. Or monsters like mind flayers and medusas that create a unique type of tension, something elevated beyond, "Will it manage to rip me apart."
That said, even a chupacabra can be good when the monster has an interesting ecology, and you can notice its presence and maybe do something to avoid a conflict, that's at least a fun mental challenge, so long as it's not rote. The first time a player learns about what a troll is, and sees it refusing to die, that's exciting. But once you know, "Oh yeah, just burn them," it's not nearly as fun.
That's why you need trolls to only attack during thunderstorms.