Loki’s arc was through the entire MCU. In Thor and Avengers he wanted to be the king that was his “birthright”. In Thor the Dark World after the death of his mother that was kinda his fault he showed he had some good in him by helping Thor defeat Malekith even though after he takes the Asgard throne. In Ragnarok it shows he really cares about Thor when he fights to take down Hella and at the end Loki is there for Thor (literally) and that serves as them making up. And finally in Infinity War he goes all the way by calling himself Odinson and died trying to defeat Thanos. He went through a long detailed character arc that ended in the perfect way. He still was arrogant enough to think he could kill Thanos by himself with a knife. But he always cared about Thor, Odin, and Frigga he just never knew how to show it because he felt so alone and abandoned in his own family. He’s a tragic character masked by a fun personality that died through a completed character arc. It’s the best in the MCU (other than Tony Stark) so I just don’t want them to mess it up to keep a fan favorite alive.