This is already better than the current justifications but it still needs work:
The DC Multiverse is essentially a storytelling device that ties together numerous materials published over the past 80+ years. Throughout the years of publications that made up the DC Multiverse, the consistency of the verse has sparked much controversy. This is due to various changes, continuity errors, and different interpretations of them that have been written by various authors over the years.
Despite this, many efforts have been made to reconcile these various inconsistencies. For instance, Grant Morrison and Mark Waid created Hypertime in the '90s to explain multiple continuity errors away, but the concept has been used so inconsistently by writers over the years, it's devolved into a buzzword with no "official" in-universe definition. In another attempt, following the declining sales of the New 52, DC co-publishers Jim Lee and Dan Didio voted against constraining writers to strict continuity (i.e. New 52 continuity, Post-Crisis continuity, etc.) as they believed making everything canon would broaden the scope for potential stories. The issue surrounding these integrations however, is that different authors write independently of each other, often adding new concepts to the older works in general disregard of older writers' content. Though cases will arise where certain writers strive to preserve the integrity of older authors' works, irreconcilable disruptions in continuity are far more conventional for the DC Multiverse.
There have been other attempts to explain the disruptions, such as with Geoff Johns' Metaverse which aimed to rationalize the various changes taking place in the DC Multiverse. There was also Scott Snyder's attempt to undo the contradictions of the DCU with the end of Death Metal, which assembled and highlighted every DC storyline, transforming the multiverse into its own sort of Omniverse. However, even that effort was sullied within a literal year under the retcons of Dark Crisis.
All in all, the above circumstances have created the following irreconcilable difficulties: