Piccolo is a character who has gone through a ton of change throughout the Dragon Ball series, from his days as the ruthless 'Demon King' Piccolo to battling Cell as the Namekian 'Who Has Long Since Forgotten His Name,' but his role as a fighter has steadily diminished as time goes on. In the Majin Buu Arc, Piccolo is little more than a glorified babysitter for Goten and Trunks, and stays on the sidelines for most of the action. If that wasn’t bad enough, Dragon Ball Super managed to completely lose sight of Piccolo’s character and abilities, effectively turning him into one big joke.
Near the end of the original Dragon Ball manga, Piccolo was introduced as the spawn of 'Daimyo' Piccolo, the evil demon king and villainous counterpart to Kami the guardian of Earth. Piccolo’s motivations were clear - he was going to try and pick up where his father left off and finish conquering the world and subjugating humanity. Entering Dragon Ball Z and the Saiyan Saga, Piccolo’s character continued to evolve as he not only allowed himself to team up with Son Goku but went on to train Son Gohan as well. Piccolo’s character arc peaked when he sacrificed himself to save the son of his archnemesis, revealing that unlike his father, Piccolo was capable of empathy and valued Gohan as a friend.
In contrast to this steady, believable growth, Dragon Ball Super instead turns Piccolo into a caricature of his most iconic moments. For starters, Piccolo's arm is ripped off a ridiculous amount of times. His arm is blown or torn off once in Resurrection F, once when sparring with Gohan, and once in the Tournament of Power, turning the injury into a running gag. Piccolo’s reputation as an efficient and intelligent fighter is also tarnished in the Universe 6 Tournament, where Piccolo is chosen to represent Universe 7, only to be completely embarrassed in his match against Frost. Goku even tells Piccolo that he practically has no shot at winning this battle, cementing his place as a sideman.
All Piccolo manages to do in this fight is jump around the ring a bunch of times while charging a Special Beam Cannon that fails to connect (a move which is presented as tactical genius, despite clearly being anything but.) Furthermore, in the Tournament of Power, Piccolo, the one character who has repeatedly shown to be capable of super-hearing is knocked out by an enemy who is simply "too small" for him to sense.
After Piccolo saves Gohan from Nappa in Dragon Ball Z, he seems to lose almost all his personal goals. While he does have temporary, immediate goals such as defeating Frieza or fighting Babidi, Piccolo never again has real personal goals like he did when his aim was to defeat Goku and conquer the Earth - a huge shame for fans who followed Dragon Ball's cue to become invested in the character. Additionally, Piccolo seems to lose most of his value as a fighter after the battle with Android 17. He may get involved every now and then to defeat cannon fodder, but never again is his sole fighting power relevant to stopping a major threat. Dragon Ball Super seems content with letting the former Demon King fade into irrelevance, allowing Piccolo to become a shadow of his former self rather than exploring why he continues to fight.