There is something difficult about capturing goodness in a group of beings. Even Tolkien relied greatly on contrasting goodness with easier-to-depict evil. It never quite works, though. Angels, those great warrior spirits, have deteriorated into babies and pixies in the poplar imagination. I once tried to give a better approximation in a children's sermon by asking them to imagine if lightning had a voice.
The LOTR movie Gimli is a bit unsatisfying. He is too obviously comic. Dwarves are serious, serious as stone. Yet in The Hobbit, Tolkien had already committed to drawing them as a bit ridiculous, in that first song about breaking plates. He attempts to show this with the centuries-old laughing elves as well. It never quite rang true. It seemed a stretch.
Intellectually, I accept that elves could be as he describes, with age giving them gravity but constant art and craftsmanship giving them a lightness of spirit. But their songs weren't funny. Someone else's humor, seen from the outside, never does seems all that compelling. Peter Jackson solved this by highlighting the gravity of the elves and the humor of the dwarves - the reverse of the Tolkien emphasis - but it's hard to fault him on this. Going the opposite way would perhaps be even less believable.
The realm of Faerie contains many things, including humor and tragedy we can only partly enter into. In our era, one almost has to revolt entirely against the Disney "little people" of various sorts, all too cute and buffoonish. Gimli rides a bit too close to Disney for my taste. Yet once one has put a humanoid up for view, its grotesqueries will strike us as either comic or evil; perhaps it is an inborn response. Monsters without some human attributes swollen wildly out of proportion are mere dangers, eliciting the same fear as a swamp or a cliff, but no levels of fear. It may be that the monsters in the story are humanish because they represent the parts of humanity (or ourselves) we dislike and wish to banish or overcome.
I have no advice on how to depict angels or elves better. If ten thousand years of artists and storytellers can't capture the idea of "good, but dangerous," I am unlikely to hit upon the solution.
Lewis tried it with a lion, and that captured a great deal that is missing from the Good Monsters of our stories.