While the version of Loki from the MCU (and from Marvel comics) is based upon the Loki of Norse Lore, the two of them are not exactly the same.
In the lore, he is the son of a giant (a jötunn) and a goddess. In the lore, Laufey is Loki’s goddess mother, not his giant father (like depicted in the MCU). He is also not the adopted son of Odin within the lore; instead, he and Odin are blood-brothers (but what event led to them becoming blood-brothers has been lost to time). He is the father of the wolf Fenrir, the goddess of the underworld (hel), the world serpent (who circles around Midgard, where humans live), and he is the mother of Sleipnir (the eight-legged horse used by Odin).
In the lore, he is a legitimate shape-shifter (much like most trackers from lore seemed to be), instead of being someone who uses magic to create illusions that will change his appearance (like he is presented in the MCU).
The version of him that is represented in the MCU has been confirmed to be bisexual (through a throw-away line in the Disney+ show “Loki,” where he talks about having relationships with both men and women), and there were some fans of the MCU that seemed to have problems with this revelation. These people should probably not look into the lore, since he is gender-fluid. Being a shapeshifter, gender and sexuality do not seem to be a concern that he has. If they would likely have a problem with these facts, the fact that he is also the mother of a horse would likely blow their little, suburban minds.
In the lore, he is sometimes depicted as a friend of the gods, and sometimes depicted as a nuisance to them; it is not uncommon for him to be the drinking buddy of Thor, and it is unlikely that he would have become a blood-brother to Odin if he was someone who was completely apposed to the gods and what they do. And it is not uncommon to come across stories where he gets the gods out of trouble or fixes the trouble that he had caused.
In one such story, the gods wanted to have a wall built around Asgard (the place where they lived), and it was Loki that arranged to have a dwarf that had come to Asgard to build the wall (by saying he would be given the precious things he had asked for if he built the wall by a certain date, only having the help of his stallion). When it appeared as though the wall would be finished by the date he would need to finish it by, it was Loki who made sure it would not get done (by changing himself into a mare and getting the attention of the stallion, luring it away from its work). The wall was not finished in time, and thus, the gods got the wall they wanted for free.
That being said, he is reported to also be the cause for the end of the world.
Captaining a giant ship that is filled with the souls of the dead (that he got from Helheim, the place that his daughter Hel rules over), and they fight against the gods and the souls the gods have acquired to help them. The sun and the moon are eaten by wolves, the gods and humanity (except for one man and one woman) are killed, and the whole world is reborn. So, even if he may have been friend and companion of the gods at some points (someone who helps them), he is also a great danger to them.
There are those who follow any number of the denominations of Heathenry (also sometimes called Germanic Neo-Paganism), who refuse to honor Loki while practicing their religion. These people believe that by honoring him, they are giving him an opportunity to be invited into their homes; by inviting him in, they are inviting evil in (he is considered evil by some people). Not everyone believes this, and they are willing to honor him, the same as they would any of the other gods.
It seems as though, because of his inclination toward mischief has caused people to mistrust him, to think that he is likely to do them harm. But assuming that he is going to do harm is to take away the good that he does in the world. By being a trickster, he promotes growth and change, making sure that the world does not become stagnant and atrophy. His function is necessary, even if it may not always be pleasant to have to work your way through his tricks, and without him, life would become boring.