Superman escalation in power level was the reason why he became uninteresting, somewhat cartoony, a "joke" as you call him.
Because of the soap opera-esque nature of comic books, writers have to come up with constantly progressing stories, increasingly difficult and challenging the hero, make him struggle.
So Superman, being an effigy of strenght and power, gets challenged in those aspects, by enemies increasingly overpowerfull, struggling against strenght-based problems, so by the end of the day all his problems are solved by punching harder. Punch the goon, punch the villain, punch the planet and even reality itself.
He is indestructible, but they also made him invulnerable; and that made him unrelatable. There should be some down-to-earth aspect, a human emotion that this godly being is struggling with. And then, by overcoming this he becomes the symbol of hope and example to follow.
I sincerely think that (for the exceptions of a few examples) long-runs are not the right medium for Superman. Batman normally gets away with it because of his noir stories, taking down low-level criminals, gang bosses and mostly-human rogue gallery alike. Superman can't take enemies weekly, he is too big for those narratives. You lose perspective of the character itself and what represents.